Primary 2 Mathematics Tuition in Li Hwan Close can begin with a measurement comparison: a fictional bag has mass 850 g and another has mass 675 g. The first is heavier by 175 g. A correct child should compare the gram quantities, understand the term heavier, calculate the difference and label the result in grams.
Li Hwan Close families choosing weekday or weekend Mathematics tuition should distinguish a measurement-reading error from a regrouping error. A learner might know that 850 is greater than 675 but borrow incorrectly when calculating the difference; another might add the masses rather than subtract for how much heavier. Different first errors call for different tutoring responses.
Singapore’s Primary 2 Mathematics syllabus includes measuring, comparing and ordering masses in kilograms and grams and whole-number subtraction within one thousand. This guide uses two measurements already expressed in grams, allowing age-appropriate subtraction without requiring compound-unit conversion before the pupil is ready.
Primary 2 Mathematics: the worked learning and parent decision framework
Compare two mass values in grams
The fictional heavier bag has a mass of 850 g and the lighter bag 675 g. Both measurements use grams, so a direct whole-number comparison is meaningful. Eight hundreds exceed six hundreds, making 850 g the larger mass.
To answer how much heavier, subtract the lighter mass from the heavier: 850 − 675 = 175 g. The result is a difference, not the total combined mass of both bags.
The addition check is 675 + 175 = 850 g. A complete answer reads, ‘The first bag is 175 grams heavier.’
At this level, keeping the given amounts in grams avoids a compound kg-and-g conversion that belongs more naturally to later measurement work.
Read measurement units before choosing an operation
Mass tells how much matter a measured object contains and is commonly expressed in grams or kilograms. The symbol g after both numbers identifies grams as the shared unit.
Ask the child to point to the given heavier and lighter amounts and identify which quantity the final question asks for. ‘How much heavier’ requests a gap, not a sum.
An answer of 1,525 g comes from adding 850 and 675. That would represent a combined mass if both bags were joined, but it is not the amount by which one exceeds the other.
A child who cannot read the abbreviation g may need vocabulary support before arithmetic. Record the first response separately from the written subtraction.
Use a comparison bar with an extra segment
Draw one bar of 675 equal mass units and a second, longer bar of 850. Align their starting points rather than place the shorter in a different part of the page.
The portion of the long bar matching 675 g is not the difference. The additional unmatched segment represents the extra 175 g.
Label the relationship as 675 g + difference = 850 g. Finding the missing part through subtraction is justified by the bar, not merely by a keyword in the problem.
Ask the learner to point to the missing section before writing a number sentence. This separates understanding of comparison from computation.
Subtract with regrouping correctly
Align the numerals 850 and 675 in hundreds, tens and ones columns. There are zero ones in 850, so exchange one of its five tens into ten ones, leaving four tens.
Subtract five ones from ten to obtain five ones. Four tens are insufficient to remove seven tens, so exchange one of the eight hundreds into ten tens, yielding fourteen tens.
Fourteen minus seven gives seven tens; seven hundreds remain after the exchange, and seven minus six leaves one hundred. The result is 175 g.
A pupil who leaves eight hundreds after the second exchange has counted one hundred twice. Use base-ten cards to connect each written carrying mark to a real exchange.
Count up to check the mass gap
Start at the lighter 675 g. Add 25 g to reach 700 g, then add 150 g to reach 850 g.
The total distance is 25 + 150 = 175 g. This confirms the subtraction by a different route without requiring a second copy of the same column algorithm.
A convenient extension can use 675 to 800 by 125 and 800 to 850 by 50; those jumps also total 175 g.
Ask why both routes are valid. They measure the same gap between two fixed quantities, simply choosing different intermediate landmarks.
Mass comparisons are not combined-weight problems
If the question changes to ‘What is the total mass of both bags?’, the appropriate calculation is 850 + 675 = 1,525 g. That is a different question from ‘how much heavier’.
Ask the child to match each answer with the words ‘combined’ and ‘difference’ rather than regard every number sentence as interchangeable.
Some pupils may select the larger 850 g as the answer to how much heavier. That names the heavier bag’s full mass, not the extra mass beyond the lighter bag.
A good tutor keeps the labels visible until the pupil can independently distinguish total, heavier mass and difference.
Check reasonableness and the written unit
The difference between 850 and 675 is less than 850 and is also less than two hundred. A result of 875 g would be implausible because it exceeds the total mass of the heavier bag.
Since both original measurements are in grams, the difference should be reported in grams. An unlabelled 175 or an incorrect 175 kg is incomplete.
Ask the child to use the inverse 675 + 175 = 850, then describe which quantity was restored. This links numerical checking with the physical story.
A correct answer should remain correct if the bags are swapped in the question: ‘How much lighter is the second?’ still gives a magnitude of 175 g.
The first wrong answer shows the next teaching need
A result of 1,525 g may be a story-interpretation error; the learner added both masses instead of comparing them. A result of 185 g may be a regrouping slip in the tens column.
A response of 850 g to the difference question may identify the larger amount but not the gap. A response of 175 kg may indicate a measurement-unit misunderstanding.
An arithmetic answer of 175 without a physical or drawn explanation may still be correct, but a new problem with changed numbers can test whether the child understands the relation.
Parents should ask for the earliest incorrect decision, not just a corrected final numeral.
Weekday class decisions
A weekday tutorial may use a current Primary 2 measurement worksheet. The first uncorrected response can show whether mass units or the comparison operation caused difficulty.
Confirm the actual teaching venue and travel; Li Hwan Close is a residential street, not a claim of an eduKate tuition room. Meals, school dismissal, homework, sport and sleep affect learning readiness.
A short focused lesson can show a comparison bar, one regrouping calculation and one inverse check, then test an unfamiliar mass pair after a delay.
The timetable should support concentration rather than simply occupy another available hour.
Weekend modelling and family routine
A weekend lesson may give more time to use labelled mass cards or a simple visual balance comparison before arithmetic. It need not involve weighing real household objects to explain the given values.
Weekend sport, family events and other enrichment can also be tiring. Choose the actual child’s settled learning period and confirm the journey.
After a physical model, move to a written problem with new gram values and a complete answer label. The later independent problem shows whether the lesson transferred.
The objective is a reliable relationship between measured quantities, not just increased worksheet volume.
Three-pupil feedback and checkpoints
One pupil may identify the larger mass correctly but subtract incorrectly; another may calculate correctly but answer a combined-mass question; a third may use an incorrect unit.
The tutor can provide distinct prompts about the comparison bar, regrouping or the gram label while preserving each child’s first independent attempt.
Progress can move from comparing gram values, to subtraction with renaming, to inverse checks, and finally to unfamiliar mass pairs after a delay.
Keep a short record of the first response, first helpful hint and independent later answer. This flexible review sequence should follow the child’s real school topic rather than promise a fixed mastery date.
What the parent should ask before choosing a tutor
A reliable three-pupil Mathematics tutorial begins with a child’s first unsupported response, one carefully selected representation and an independent new question after a short delay. The exact weekday or weekend should be chosen for readiness, realistic travel and sufficient rest, not because a neighbourhood title implies a new tuition branch.
The MOE Primary Mathematics syllabus updated October 2025, eduKate Mathematics learning hub and Li Hwan Close street reference give curriculum and location context. The street is a residential area near Lorong Chuan, not a claimed teaching venue. Ask directly for available class times, teaching address, fees and appropriate 3-pax placement.
Primary 2 independently checked practice bank — part one
Every task in this bank is fictional and should be tried before the written solution is read. The teaching objective is to explain quantities and units, select an appropriate relationship, calculate and verify with a genuinely different representation. Success on a changed question after a delay is stronger evidence than recalling the original worked answer.
1. Compare fictional masses 850 g and 675 g
First interpretation: two imaginary bags have masses of 850 grams and 675 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 850 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 850 − 675 = 175 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 675-g matching section inside the 850-g whole and a remaining segment of 175 g. The answer sentence is, “The first bag is 175 g heavier.”
Count-up verification: from 675 g, add 25 g to reach a convenient 700-g benchmark, then add another 150 g to reach 850 g. The jumps total 25 + 150 = 175 g, agreeing with the subtraction. An inverse calculation adds 675 + 175 to recover 850; the model and arithmetic should show one continuous gap.
A common mistake is to add 850 and 675, producing a combined mass rather than a comparison, or to report 175 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 840 g and the gap becomes 165 g. If the lighter bag instead gains five grams, it becomes 680 g and the gap becomes 170 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
2. Compare fictional masses 920 g and 785 g
First interpretation: two imaginary bags have masses of 920 grams and 785 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 920 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 920 − 785 = 135 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 785-g matching section inside the 920-g whole and a remaining segment of 135 g. The answer sentence is, “The first bag is 135 g heavier.”
Count-up verification: from 785 g, add 15 g to reach a convenient 800-g benchmark, then add another 120 g to reach 920 g. The jumps total 15 + 120 = 135 g, agreeing with the subtraction. An inverse calculation adds 785 + 135 to recover 920; the model and arithmetic should show one continuous gap.
A common mistake is to add 920 and 785, producing a combined mass rather than a comparison, or to report 135 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 910 g and the gap becomes 125 g. If the lighter bag instead gains five grams, it becomes 790 g and the gap becomes 130 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
3. Compare fictional masses 740 g and 565 g
First interpretation: two imaginary bags have masses of 740 grams and 565 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 740 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 740 − 565 = 175 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 565-g matching section inside the 740-g whole and a remaining segment of 175 g. The answer sentence is, “The first bag is 175 g heavier.”
Count-up verification: from 565 g, add 35 g to reach a convenient 600-g benchmark, then add another 140 g to reach 740 g. The jumps total 35 + 140 = 175 g, agreeing with the subtraction. An inverse calculation adds 565 + 175 to recover 740; the model and arithmetic should show one continuous gap.
A common mistake is to add 740 and 565, producing a combined mass rather than a comparison, or to report 175 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 730 g and the gap becomes 165 g. If the lighter bag instead gains five grams, it becomes 570 g and the gap becomes 170 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
4. Compare fictional masses 690 g and 485 g
First interpretation: two imaginary bags have masses of 690 grams and 485 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 690 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 690 − 485 = 205 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 485-g matching section inside the 690-g whole and a remaining segment of 205 g. The answer sentence is, “The first bag is 205 g heavier.”
Count-up verification: from 485 g, add 15 g to reach a convenient 500-g benchmark, then add another 190 g to reach 690 g. The jumps total 15 + 190 = 205 g, agreeing with the subtraction. An inverse calculation adds 485 + 205 to recover 690; the model and arithmetic should show one continuous gap.
A common mistake is to add 690 and 485, producing a combined mass rather than a comparison, or to report 205 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 680 g and the gap becomes 195 g. If the lighter bag instead gains five grams, it becomes 490 g and the gap becomes 200 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
5. Compare fictional masses 810 g and 645 g
First interpretation: two imaginary bags have masses of 810 grams and 645 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 810 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 810 − 645 = 165 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 645-g matching section inside the 810-g whole and a remaining segment of 165 g. The answer sentence is, “The first bag is 165 g heavier.”
Count-up verification: from 645 g, add 55 g to reach a convenient 700-g benchmark, then add another 110 g to reach 810 g. The jumps total 55 + 110 = 165 g, agreeing with the subtraction. An inverse calculation adds 645 + 165 to recover 810; the model and arithmetic should show one continuous gap.
A common mistake is to add 810 and 645, producing a combined mass rather than a comparison, or to report 165 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 800 g and the gap becomes 155 g. If the lighter bag instead gains five grams, it becomes 650 g and the gap becomes 160 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
6. Compare fictional masses 950 g and 775 g
First interpretation: two imaginary bags have masses of 950 grams and 775 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 950 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 950 − 775 = 175 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 775-g matching section inside the 950-g whole and a remaining segment of 175 g. The answer sentence is, “The first bag is 175 g heavier.”
Count-up verification: from 775 g, add 25 g to reach a convenient 800-g benchmark, then add another 150 g to reach 950 g. The jumps total 25 + 150 = 175 g, agreeing with the subtraction. An inverse calculation adds 775 + 175 to recover 950; the model and arithmetic should show one continuous gap.
A common mistake is to add 950 and 775, producing a combined mass rather than a comparison, or to report 175 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 940 g and the gap becomes 165 g. If the lighter bag instead gains five grams, it becomes 780 g and the gap becomes 170 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
7. Compare fictional masses 800 g and 625 g
First interpretation: two imaginary bags have masses of 800 grams and 625 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 800 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 800 − 625 = 175 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 625-g matching section inside the 800-g whole and a remaining segment of 175 g. The answer sentence is, “The first bag is 175 g heavier.”
Count-up verification: from 625 g, add 75 g to reach a convenient 700-g benchmark, then add another 100 g to reach 800 g. The jumps total 75 + 100 = 175 g, agreeing with the subtraction. An inverse calculation adds 625 + 175 to recover 800; the model and arithmetic should show one continuous gap.
A common mistake is to add 800 and 625, producing a combined mass rather than a comparison, or to report 175 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 790 g and the gap becomes 165 g. If the lighter bag instead gains five grams, it becomes 630 g and the gap becomes 170 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
8. Compare fictional masses 780 g and 598 g
First interpretation: two imaginary bags have masses of 780 grams and 598 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 780 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 780 − 598 = 182 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 598-g matching section inside the 780-g whole and a remaining segment of 182 g. The answer sentence is, “The first bag is 182 g heavier.”
Count-up verification: from 598 g, add 2 g to reach a convenient 600-g benchmark, then add another 180 g to reach 780 g. The jumps total 2 + 180 = 182 g, agreeing with the subtraction. An inverse calculation adds 598 + 182 to recover 780; the model and arithmetic should show one continuous gap.
A common mistake is to add 780 and 598, producing a combined mass rather than a comparison, or to report 182 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 770 g and the gap becomes 172 g. If the lighter bag instead gains five grams, it becomes 603 g and the gap becomes 177 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
9. Compare fictional masses 905 g and 758 g
First interpretation: two imaginary bags have masses of 905 grams and 758 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 905 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 905 − 758 = 147 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 758-g matching section inside the 905-g whole and a remaining segment of 147 g. The answer sentence is, “The first bag is 147 g heavier.”
Count-up verification: from 758 g, add 42 g to reach a convenient 800-g benchmark, then add another 105 g to reach 905 g. The jumps total 42 + 105 = 147 g, agreeing with the subtraction. An inverse calculation adds 758 + 147 to recover 905; the model and arithmetic should show one continuous gap.
A common mistake is to add 905 and 758, producing a combined mass rather than a comparison, or to report 147 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 895 g and the gap becomes 137 g. If the lighter bag instead gains five grams, it becomes 763 g and the gap becomes 142 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
10. Compare fictional masses 630 g and 455 g
First interpretation: two imaginary bags have masses of 630 grams and 455 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 630 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 630 − 455 = 175 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 455-g matching section inside the 630-g whole and a remaining segment of 175 g. The answer sentence is, “The first bag is 175 g heavier.”
Count-up verification: from 455 g, add 45 g to reach a convenient 500-g benchmark, then add another 130 g to reach 630 g. The jumps total 45 + 130 = 175 g, agreeing with the subtraction. An inverse calculation adds 455 + 175 to recover 630; the model and arithmetic should show one continuous gap.
A common mistake is to add 630 and 455, producing a combined mass rather than a comparison, or to report 175 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 620 g and the gap becomes 165 g. If the lighter bag instead gains five grams, it becomes 460 g and the gap becomes 170 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
11. Compare fictional masses 745 g and 569 g
First interpretation: two imaginary bags have masses of 745 grams and 569 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 745 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 745 − 569 = 176 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 569-g matching section inside the 745-g whole and a remaining segment of 176 g. The answer sentence is, “The first bag is 176 g heavier.”
Count-up verification: from 569 g, add 31 g to reach a convenient 600-g benchmark, then add another 145 g to reach 745 g. The jumps total 31 + 145 = 176 g, agreeing with the subtraction. An inverse calculation adds 569 + 176 to recover 745; the model and arithmetic should show one continuous gap.
A common mistake is to add 745 and 569, producing a combined mass rather than a comparison, or to report 176 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 735 g and the gap becomes 166 g. If the lighter bag instead gains five grams, it becomes 574 g and the gap becomes 171 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
12. Compare fictional masses 870 g and 690 g
First interpretation: two imaginary bags have masses of 870 grams and 690 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 870 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 870 − 690 = 180 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 690-g matching section inside the 870-g whole and a remaining segment of 180 g. The answer sentence is, “The first bag is 180 g heavier.”
Count-up verification: from 690 g, add 10 g to reach a convenient 700-g benchmark, then add another 170 g to reach 870 g. The jumps total 10 + 170 = 180 g, agreeing with the subtraction. An inverse calculation adds 690 + 180 to recover 870; the model and arithmetic should show one continuous gap.
A common mistake is to add 870 and 690, producing a combined mass rather than a comparison, or to report 180 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 860 g and the gap becomes 170 g. If the lighter bag instead gains five grams, it becomes 695 g and the gap becomes 175 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
13. Compare fictional masses 920 g and 805 g
First interpretation: two imaginary bags have masses of 920 grams and 805 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 920 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 920 − 805 = 115 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 805-g matching section inside the 920-g whole and a remaining segment of 115 g. The answer sentence is, “The first bag is 115 g heavier.”
Count-up verification: from 805 g, add 95 g to reach a convenient 900-g benchmark, then add another 20 g to reach 920 g. The jumps total 95 + 20 = 115 g, agreeing with the subtraction. An inverse calculation adds 805 + 115 to recover 920; the model and arithmetic should show one continuous gap.
A common mistake is to add 920 and 805, producing a combined mass rather than a comparison, or to report 115 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 910 g and the gap becomes 105 g. If the lighter bag instead gains five grams, it becomes 810 g and the gap becomes 110 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
14. Compare fictional masses 660 g and 475 g
First interpretation: two imaginary bags have masses of 660 grams and 475 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 660 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 660 − 475 = 185 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 475-g matching section inside the 660-g whole and a remaining segment of 185 g. The answer sentence is, “The first bag is 185 g heavier.”
Count-up verification: from 475 g, add 25 g to reach a convenient 500-g benchmark, then add another 160 g to reach 660 g. The jumps total 25 + 160 = 185 g, agreeing with the subtraction. An inverse calculation adds 475 + 185 to recover 660; the model and arithmetic should show one continuous gap.
A common mistake is to add 660 and 475, producing a combined mass rather than a comparison, or to report 185 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 650 g and the gap becomes 175 g. If the lighter bag instead gains five grams, it becomes 480 g and the gap becomes 180 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
15. Compare fictional masses 710 g and 555 g
First interpretation: two imaginary bags have masses of 710 grams and 555 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 710 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 710 − 555 = 155 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 555-g matching section inside the 710-g whole and a remaining segment of 155 g. The answer sentence is, “The first bag is 155 g heavier.”
Count-up verification: from 555 g, add 45 g to reach a convenient 600-g benchmark, then add another 110 g to reach 710 g. The jumps total 45 + 110 = 155 g, agreeing with the subtraction. An inverse calculation adds 555 + 155 to recover 710; the model and arithmetic should show one continuous gap.
A common mistake is to add 710 and 555, producing a combined mass rather than a comparison, or to report 155 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 700 g and the gap becomes 145 g. If the lighter bag instead gains five grams, it becomes 560 g and the gap becomes 150 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
16. Compare fictional masses 845 g and 695 g
First interpretation: two imaginary bags have masses of 845 grams and 695 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 845 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 845 − 695 = 150 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 695-g matching section inside the 845-g whole and a remaining segment of 150 g. The answer sentence is, “The first bag is 150 g heavier.”
Count-up verification: from 695 g, add 5 g to reach a convenient 700-g benchmark, then add another 145 g to reach 845 g. The jumps total 5 + 145 = 150 g, agreeing with the subtraction. An inverse calculation adds 695 + 150 to recover 845; the model and arithmetic should show one continuous gap.
A common mistake is to add 845 and 695, producing a combined mass rather than a comparison, or to report 150 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 835 g and the gap becomes 140 g. If the lighter bag instead gains five grams, it becomes 700 g and the gap becomes 145 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
17. Compare fictional masses 735 g and 488 g
First interpretation: two imaginary bags have masses of 735 grams and 488 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 735 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 735 − 488 = 247 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 488-g matching section inside the 735-g whole and a remaining segment of 247 g. The answer sentence is, “The first bag is 247 g heavier.”
Count-up verification: from 488 g, add 12 g to reach a convenient 500-g benchmark, then add another 235 g to reach 735 g. The jumps total 12 + 235 = 247 g, agreeing with the subtraction. An inverse calculation adds 488 + 247 to recover 735; the model and arithmetic should show one continuous gap.
A common mistake is to add 735 and 488, producing a combined mass rather than a comparison, or to report 247 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 725 g and the gap becomes 237 g. If the lighter bag instead gains five grams, it becomes 493 g and the gap becomes 242 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
18. Compare fictional masses 680 g and 507 g
First interpretation: two imaginary bags have masses of 680 grams and 507 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 680 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 680 − 507 = 173 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 507-g matching section inside the 680-g whole and a remaining segment of 173 g. The answer sentence is, “The first bag is 173 g heavier.”
Count-up verification: from 507 g, add 93 g to reach a convenient 600-g benchmark, then add another 80 g to reach 680 g. The jumps total 93 + 80 = 173 g, agreeing with the subtraction. An inverse calculation adds 507 + 173 to recover 680; the model and arithmetic should show one continuous gap.
A common mistake is to add 680 and 507, producing a combined mass rather than a comparison, or to report 173 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 670 g and the gap becomes 163 g. If the lighter bag instead gains five grams, it becomes 512 g and the gap becomes 168 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
19. Compare fictional masses 930 g and 745 g
First interpretation: two imaginary bags have masses of 930 grams and 745 grams. Ask which bag is heavier and how much heavier, with one initial answer recorded before teaching. Both quantities already use grams; there is no need to invent a compound kilogram conversion. The comparison first identifies 930 as the larger measurement, then finds the gap rather than joining the bags.
Worked subtraction: 930 − 745 = 185 g. The larger mass is reduced by the lighter mass to measure the extra amount. A comparison bar should show a 745-g matching section inside the 930-g whole and a remaining segment of 185 g. The answer sentence is, “The first bag is 185 g heavier.”
Count-up verification: from 745 g, add 55 g to reach a convenient 800-g benchmark, then add another 130 g to reach 930 g. The jumps total 55 + 130 = 185 g, agreeing with the subtraction. An inverse calculation adds 745 + 185 to recover 930; the model and arithmetic should show one continuous gap.
A common mistake is to add 930 and 745, producing a combined mass rather than a comparison, or to report 185 kg after calculating in grams. Another pupil may identify the larger bag correctly but lose a borrowed ten while subtracting. Ask for the first mistaken step and separate measurement vocabulary, the story’s question, place-value arithmetic and unit labelling.
Transfer changes the quantities instead of repeating the same answer: if the heavier bag becomes ten grams lighter, its mass is 920 g and the gap becomes 175 g. If the lighter bag instead gains five grams, it becomes 750 g and the gap becomes 180 g. The pupil should predict the direction of the change, then verify by subtraction. Keep the first unassisted response and minimal hint.
Mass-comparison questions for Li Hwan Close parents
How much heavier is 850 g than 675 g?
The difference is 175 g because 850 − 675 = 175 and 675 + 175 = 850.
Why is addition not the correct operation?
Adding the two masses finds a combined weight, whereas ‘how much heavier’ asks for the gap between measurements.
Does the child need to convert to kilograms?
No. Both given masses are already in grams, so they can be compared and subtracted in the same unit.
Is measuring mass taught in Primary 2?
Yes. The updated Primary 2 Mathematics syllabus covers measuring and comparing masses in kilograms and grams.
What is the best independent check?
Count up from the lighter mass to a convenient hundred, then to the heavier value, and add the jumps.
Should parents choose weekday or weekend tuition?
Choose the time when the learner can explain the measurement and perform a new comparison with adequate attention and rest.
Choose the tutor from the first learning gap
For the current official scope, consult the 2021 MOE Primary Mathematics syllabus updated October 2025. The eduKate Mathematics learning hub provides other topic explanations. This worked guide is an original learning example, not a grade guarantee or a claim about results achieved by actual children.
Li Hwan Close is a real residential street in the wider Serangoon Garden and Lorong Chuan area, documented by URA street planning records. Nothing in this article establishes an eduKate teaching branch or currently available class on Li Hwan Close. Ask for the actual venue, fee structure, suitable 3-pax placement and door-to-door journey from the child’s home or school before committing to weekday or weekend tuition.
Use a parent–student consultation to discuss a recent uncorrected Primary 2 Mathematics question and the first hint that helped. For another example at the same school level, see Primary 2 Mathematics Tuition | Li Hwan Drive. The choice of day should preserve meals, schoolwork, sleep and a small later independent check.
Continue across the Li Hwan Close Primary Mathematics guides
Each year-level guide develops a different MOE-aligned Mathematics concept, a fully worked first example, independent new questions and practical weekday-versus-weekend scheduling guidance. These pages are local learning resources, not claims of separate eduKate classrooms on the residential street.
- Primary 1: Number patterns and checking steps
- Primary 3: Litres and millilitres
- Primary 4: Composite area and perimeter
Compare a different concept at the same grade in Primary 2 Mathematics Tuition | Li Hwan Drive, or follow the broader eduKate Mathematics learning hub. Confirm the actual available tuition venue, timetable, 3-pax placement and travel directly before booking.