“Sixty-three pencils, and twenty are put away. How many remain?” A Primary 1 child can know every numeral in 63 − 20 yet still answer forty-one or forty-three for different reasons. For families around Serangoon North Avenue 2 comparing weekday and weekend Mathematics tuition, the useful starting point is whether the learner understands what subtracting two tens means.
The correct answer is 43 pencils. Sixty-three is six tens and three ones; taking away twenty removes two complete tens but leaves the original three ones. A pupil who can show that with counters and explain the outcome has a useful foundation for later subtraction.
The lesson should not become a race through written algorithms. Singapore’s Primary 1 Mathematics progression includes understanding numbers within one hundred and addition and subtraction in familiar quantities. A calm, well-timed three-pupil tutorial can repair a missing place-value idea and check it on a new example rather than only marking answers right and wrong.
Find the next useful step
The answer and its meaning · Check the starting point · Understand a worked model · Explain and verify · Diagnose misconceptions · Weekday versus weekend · What three-pupil teaching should do · Four-week checks · Independent transfer question · Parent questions · Arrange learning support
Start with six tens and three ones; the result is four tens and three ones
Represent sixty-three with six bundles of ten sticks and three separate sticks. Ask how many sticks there are before anything is taken away. Six full tens make sixty, with three more making sixty-three.
The instruction is to remove twenty pencils. Twenty is not two individual pencils: it means two complete bundles of ten. Lift two whole bundles away from the original six.
Four ten-bundles remain, plus the same three loose sticks. That collection represents 40 + 3 = 43, so 63 − 20 = 43.
A short verbal explanation is, “Sixty-three is six tens and three ones. I remove two tens, leaving four tens and three ones.” Each phrase corresponds to a visible change in the model.
A second check is 43 + 20 = 63. Returning the two removed bundles restores the initial quantity. Addition provides a reason for the answer instead of merely repeating the subtraction.
The ability to tell what stayed unchanged—the three ones—is important. Subtracting a multiple of ten in this example changes the tens count, not the value of the loose ones.
Identify place value before teaching a subtraction method
Put the numeral 63 on a card and ask the learner what the digit six represents. The answer is sixty or six tens, not six individual pencils. The three represents three ones.
Ask the child to build the number from a ten-frame or base-ten materials. They should be able to show six full groups of ten and another three objects without reciting sixty-three as a sound alone.
Next place the numeral 20 beside it. Ask whether taking away twenty is the same as removing two. It is not; twenty is ten times as many as two. Compare two loose counters with two full ten-bundles to make the difference visible.
The pupil may know 6 − 2 = 4 but not understand why that fact can be used here. Link the calculation to bundles: six groups of ten minus two groups of ten leaves four groups of ten.
A common starting error is counting each of the sixty-three pencils individually. That can eventually give the answer, but the purpose of the model is to make quantities organised into tens so the child can reason more efficiently.
Another learner may remove two full bundles but then forget the three ones. Ask where the loose objects were placed. They were never removed, so they remain part of the answer.
Preserve the first drawing or physical arrangement. If the child can build both given numbers accurately, the focus may be selecting what gets removed; if even sixty-three is represented wrongly, place value is the earlier learning priority.
Draw a tens-and-ones chart and connect it with the equation
Draw two columns with headings “Tens” and “Ones”. Place six dots in the tens column, each standing for one ten, and three separate dots in the ones column, each standing for one.
Record the beginning as six tens and three ones. The value is 6 × 10 + 3 = 63. Even if multiplication notation is introduced gently, the spoken meaning should remain clear.
Strike through two of the six tens dots because twenty is two tens. Do not strike through any ones dots. Four tens dots and three ones dots remain.
Write the resulting value as 4 × 10 + 3 = 43. The written numeral forty-three agrees with the objects and the chart.
Now write the subtraction 63 − 20 = 43 underneath. Point to each given number in the chart and explain why the twenty is removed from the tens, not from the ones.
A number line offers an alternate representation: begin at 63, jump back ten to 53, and back ten again to 43. Two jumps of ten represent the full twenty removed.
The number-line route and the chart are equivalent. One tracks the change in total value, while the other shows what happens to tens and ones.
A tempting but incorrect method is subtracting the digit two from the ones digit three because both appear in the written question. That would ignore that the two is in the tens position of 20, where it stands for twenty, not two.
Ask the learner to show the same calculation with counters, chart and line. The ability to connect these methods is a stronger sign of understanding than choosing a particular preferred drawing.
Check the result by addition and a changed story
Suppose forty-three pencils remain after twenty were put away. How many pencils were present initially? Recombine the parts: forty-three plus twenty equals sixty-three.
The check 43 + 20 = 63 shows that none of the original three loose pencils was lost when the two tens were removed.
Change the object in the story: “There are sixty-three library bookmarks. Twenty are distributed. How many are left?” The answer is still forty-three because the mathematical relationship has not changed.
A pupil should identify that the names of the objects are not the numbers being manipulated. The operation depends on the fact that a set of sixty-three loses twenty, not on pencils or bookmarks.
Ask for an estimate first. The answer should be less than sixty-three and more than thirty because only two of the six ten-bundles were removed. A result such as six or eighty-three is unreasonable.
As a small extension, compare 63 − 2 = 61 with 63 − 20 = 43. Those two results differ because two and twenty represent different place-value quantities.
The pupil’s complete answer should include a quantity label such as “forty-three pencils remain.” A numerically correct response without the context label is developing competence but can still be improved.
Different mistakes call for different interventions
An answer of sixty-one likely comes from subtracting two individual pencils rather than two tens. The tutor should contrast 2 and 20 with loose counters and tied bundles.
An answer of forty may mean the child correctly removed two tens but failed to include the three remaining ones. Return to the chart and identify what was not crossed out.
An answer of forty-one can arise from an inconsistent digit-by-digit subtraction. Ask the pupil to explain what each digit in 63 and 20 represents before trying the calculation again.
A child who draws six tens and three ones correctly but writes thirty-four may have reversed the numeral’s tens and ones places. The tutor can point from the model to the written columns and ask for a correction.
An answer greater than sixty-three is unreasonable for taking away twenty pencils. Ask whether removing objects could leave more than the original set under the described story.
If the learner finds forty-three after copying the teacher’s chart but cannot do a new subtraction alone, record that as guided progress rather than independent mastery. A different number is needed to test transfer.
A good tutor identifies the first unstable decision instead of prescribing the same twenty sums to every learner who answered incorrectly. The distinction between place value, number representation, operation choice and basic subtraction matters.
Compare the real weekday and weekend learning windows
A weekday Primary 1 tutorial may help soon after the child encounters tens and ones in school. The pupil can bring an uncorrected place-value exercise so the tutor sees whether the first difficulty was reading the numeral or subtracting the right unit.
But an available hour after school does not necessarily mean the child is ready to concentrate. Factor in meals, school dismissal, the trip to the confirmed teaching venue and the journey home before bedtime.
For a Serangoon North Avenue 2 family, a locality label does not establish the location of a particular eduKate class. Confirm the actual centre address and route rather than assuming a session operates at a nearby bus stop or building.
A weekend class can offer a slower start with base-ten sticks, a ten-frame and a spoken subtraction story. That can help young learners who need to move the objects before trusting a written equation.
However, a weekend already filled with sport, family visits and other enrichment may be just as exhausting. Compare the child’s actual attention, not simply the name of the day.
The correct choice includes a small independent revisit several days later. When a child solves one new tens subtraction without the tutor’s model, the family can see whether the concept persisted.
| Decision factor | Weekday | Weekend |
|---|---|---|
| Attention after school | A recent school place-value exercise may be fresh, but meals and travel matter | Potentially calmer modelling, but weekend commitments can also cause fatigue |
| Teaching materials | Brief focused bundle-and-chart work | More room for counters and explanation if needed |
| Review | New tens subtraction on another day | Short fresh problem during the school week |
Use a three-pupil class to diagnose the first missing idea
One learner might remove two individual sticks instead of twenty; another might remove the right bundles but forget the ones; a third might build and remove correctly but write the answer’s digits in the wrong order.
These pupils do not have the same problem. The first needs recognition of a ten as a grouped unit. The second needs to track the unchanged ones. The third needs a bridge from the model to the written numeral.
Ask every pupil for an independent first attempt before displaying the correct result. A group of three can support differentiated feedback only when each child’s reasoning remains visible.
A useful prompt might be “Show me the twenty you are removing” rather than “Subtract two from six.” That guides the student towards interpreting the mathematical quantity without supplying the numerical answer.
The next pupil may instead need “What happened to the three loose ones?” A small hint tailored to the error is more effective than repeating a full explanation to the group.
Gradually remove support: start with ten-bundles, move to a labelled place-value chart, then present a new written equation and ask the pupil to explain it alone.
Parents can ask how the tutor checked the child’s explanation rather than merely the final numeral. The Primary 1 counting and place-value study guide links this activity to broader early-primary number sense.
Four learning checks without overloading the week
In week one, establish what tens and ones mean. A short first attempt at representing sixty-three can reveal whether the number has been read correctly.
Week two can use subtracting multiples of ten without regrouping, such as 63 − 20, allowing the child to connect bundles with a written numeral.
Week three can contrast taking away twenty with taking away two, so the pupil must use the actual value of the subtracted number rather than the presence of the digit two.
In week four, introduce an unfamiliar number after a delay and ask for an unsupported model or equation. The pupil should choose the units to remove rather than wait for the adult to name them.
Keep the record small: initial answer, first hint, corrected explanation and later independent attempt. Parents do not need to add a long home worksheet every day.
If numeral reading is still unstable, return to grouping by tens. If that is secure but a subtraction fact fails, practise that exact relationship separately.
This is an adjustable review route, not a guarantee that mastery occurs after a fixed number of lessons. The child’s current schoolwork and attention should direct the pace.
Try 78 − 30 and 54 − 10 without the original answer visible
On another day, give the learner 78 − 30. Seventy-eight is seven tens and eight ones. Removing three tens leaves four tens and eight ones.
Therefore 78 − 30 = 48. Check by 48 + 30 = 78. The eight ones stayed unchanged because only full tens were removed.
Then ask for 54 − 10. Five tens and four ones become four tens and four ones, so the answer is 44.
A contrast question, 54 − 1, gives fifty-three. The child should explain why subtracting one and subtracting ten change different place values.
Ask for a full sentence in the context of a short story, such as fifty-four badges with ten removed. The final answer is forty-four badges remaining.
If the pupil repeatedly answers as if thirty were three, ask for a model before revealing the answer. The difficulty is still the value of the digits, not merely calculation speed.
Keep the first independent response and the first hint, if any. When the child can show each removed ten and verify a new answer unaided, the place-value reasoning is becoming transferable.
Frequently asked questions from Serangoon North Avenue 2 parents
What is 63 minus 20?
Forty-three. Six tens and three ones minus two tens leave four tens and three ones.
Why is 63 − 20 not the same as 63 − 2?
The numeral 20 represents two whole tens. Removing twenty gives 43, while removing two individual ones gives 61.
Should a Primary 1 child use base-ten blocks?
They are useful when the value of tens and ones is not yet secure. The goal is eventually to reason without needing physical blocks for every question.
What should parents ask a Mathematics tutor?
Ask which place-value step was wrong, what the child can now explain and how another subtraction will be checked independently.
Is a weekday or weekend tutorial more effective?
Either can be suitable. Consider the child’s alertness, the confirmed journey, rest and a realistic delayed review.
Choose the right learning support, then the right lesson day
Bring one uncorrected piece of schoolwork, the pupil’s first explanation and a note of the first hint needed. The eduKate Mathematics learning hub connects this skill with other Primary and Secondary topics. The official MOE Primary Mathematics syllabus is the reference for curriculum progression; the example here is a focused diagnostic, not a full examination or a promise of particular results.
Serangoon North Avenue 2 identifies the readers this guide addresses; it is not a claim that eduKate operates a newly opened branch or teaching room on this road. Check the confirmed venue, current availability, fees, suitability of a 3-pax group and the actual journey from school or home. For separate neighbourhood context, see Learning Serangoon North and the Serangoon primary school routes and family-learning guide.
For an eduKate parent–student consultation, share the school level, the earliest unstable step, a current piece of working and the day on which the child can arrive attentive without sacrificing meals, sleep or recovery. Ask how independent success will be checked with different numbers after the tutorial.
Explore the Serangoon North Avenue 2 Mathematics learning series
Continue through the Primary 1–4 guides for different worked problems, individual tutor diagnostics and a practical comparison of weekday and weekend learning.
- Primary 2: Odd and even numbers through equal pairs
- Primary 3: Two-step subtraction and equal sharing
- Primary 4: Rounding to tens, hundreds and thousands
For a separate neighbourhood example, see Primary 1 Mathematics Tuition | Serangoon North Avenue 1. The eduKate Mathematics learning hub provides other study routes.
Continue through Serangoon North Avenue 2 Mathematics: Primary 5: Percentage Remainders · Primary 6: Changed Averages · PSLE: L-Shape Geometry · Exam Prep: Data Tables. Each guide develops a different school-level skill.