Sec 3 G3 Maths Bukit Timah | Mobile Data Plans

Secondary 3 G3 Mathematics Tutor Bukit Timah | Mobile Data Plans: Unit Rates, Percentages and Bills — Did you know? The cheapest-looking monthly mobile data plan may become the most expensive if its overage rate is higher. A Secondary 3 G3 student can work that out with a simple combination of rates, percentages, thresholds and equations. The challenge is to separate what is included from what costs extra, then check that both plans are compared at exactly the same usage level.

Quick answer: make a billing table before calculating

Use the unit convention stated in the exercise. These examples use decimal 1 GB = 1,000 MB; binary GiB and MiB are different units.
Allowance remaining = allowance − usage when usage has not exceeded the included allowance.
Usage percentage = actual use ÷ included allowance × 100%. It may exceed 100%.
Extra data = max(0, used GB − included GB), with both measured in identical units.
Total monthly bill = stated fixed fee + extra data charge + other charges explicitly specified.
Compare total bills at the same usage under every plan’s own threshold and rate.
Round additional usage to full billing units only when the question says that whole-unit charging applies.
Read whether unused data rolls over; do not invent credits, refunds or tax conditions.

The 2027 Singapore–Cambridge SEC G3 Mathematics K310 syllabus covers ratio, percentages, rates, linear relationships, inequalities and financial word problems. Mobile data plans provide one modern fictional application. All plan costs and usage rates below are created for instruction, not actual provider offers, and the school’s chapter timing can differ from this full-course reference.

Go to: Understand the tariff · 40 worked examples · Common errors · Practice plan · FAQs.

Understand the model before selecting a rate

Fixed and variable costs

A subscription may contain a fixed monthly charge that already covers some data. Additional usage can create a variable charge only above the specified inclusion. For example, $20 for ten gigabytes plus $3 per extra gigabyte costs $20 at nine gigabytes and $29 at thirteen gigabytes. Do not bill the included data again.

The correct first question is not how many gigabytes were consumed. It is whether that consumption crossed the plan threshold, and what rate applies to the portion above it.

Decimal and binary units

In this lesson one gigabyte explicitly equals one thousand megabytes, so 2.5 GB equals 2,500 MB. Some computer contexts use GiB and MiB, which are different binary units. A real provider’s billing definitions must be checked instead of assumed from a classroom problem.

An effective tutor asks students to label both quantities before adding or dividing them. Converting to one unit is necessary even when the visible numbers look easy.

Percentages beyond 100

If data use is ten gigabytes while the included allowance is eight, usage is 10/8=125% of the allowance. The percentage is mathematically valid and describes a reference quantity exceeded by a quarter.

It does not automatically mean the provider allows unlimited overage or charges a particular amount. Those are separate conditions that the problem must state.

Plan comparison requires matched assumptions

Plan A might have a $18 basic fee with ten gigabytes included, while Plan B costs $25 with fifteen included. At twelve gigabytes, the lower basic fee may win; at eighteen, a lower marginal rate on Plan B may change the result.

A fair model calculates both bills for the same usage, including each separate threshold, rather than comparing only the fixed prices.

Bills can be piecewise functions

Under a fixed-plus-overage rule, the bill remains constant until the included allowance is used, then increases for additional data. This is a piecewise mathematical relationship, not a single per-GB multiplication from zero.

A number line showing the included interval and extra interval can make the structure clear. When a pupil sees the threshold, the algebraic model becomes easier to build.

Whole-unit billing is a condition

An invented plan may charge $3 per whole extra gigabyte, meaning 1.2 GB of overage would require two full blocks. Another fictional plan may charge proportionately, giving $3.60 for the same overage.

Do not apply a ceiling or round down without reading the given billing rule. The context controls whether the result must be a whole count.

A budget becomes an inequality

If a plan costs $20 plus $2 per extra whole gigabyte beyond eight and the budget is $30, five full extra units are affordable. The maximum is thirteen gigabytes under the model.

Check the next integer. A sixth extra gigabyte would make the bill $32, exceeding the limit. This verifies the claimed maximum.

Time can drive data consumption

If a hypothetical stream consumes sixty megabytes per minute for thirty minutes, it uses 1,800 MB or 1.8 GB under the declared decimal convention. Rate times time gives the consumed amount.

The rate is an assumed classroom value. Actual applications and networks can vary. The Mathematics skill is choosing consistent units and explaining what the calculated total represents.

Unspent data is not a refund

When a subscription includes fifteen gigabytes and the user consumes eleven, four gigabytes remain unused under that month’s simple arithmetic model. Unless rollover or refund terms are supplied, no additional cash value follows.

Do not infer an economic consequence from a remaining physical or digital allowance. Separate the quantity that remains from the financial rule used to charge it.

A check is part of a complete answer

A correct bill calculation can be reverse-checked: subtract the fixed fee, divide the remainder by the overage rate, and see whether the stated extra usage is recovered. A rate calculation can be checked by multiplying the converted total back.

Finish with a sentence identifying the chosen plan, final bill, usage and the assumptions. Mathematical communication is more helpful than an unexplained number.

40 original worked examples and checking prompts

These are constructed teaching scenarios, not official examination questions or current Singapore telecommunications offers. There are ten types of decision, each repeated with four changed inputs. Attempt the question before looking at the answer, then compare the correct unit, tariff threshold and independent checking line.

GB-to-MB conversion

This group focuses on gb-to-mb conversion. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 1. Question: Under 1 GB = 1,000 MB, convert 2 GB into MB. Method: Multiply 2×1,000=2000 MB. Check: Dividing 2000 MB by 1,000 gives 2 GB. Watch for: This exercise specifies decimal units, not GiB.

Independent transfer: State the units beside each amount before calculating. If both sides of a fraction do not use compatible data units, convert them. Then compare the result with the original allowance or rate rather than assuming the first decimal on the screen is right. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 2. Question: Under 1 GB = 1,000 MB, convert 2.5 GB into MB. Method: Multiply 2.5×1,000=2500 MB. Check: Dividing 2500 MB by 1,000 gives 2.5 GB. Watch for: This exercise specifies decimal units, not GiB.

Independent transfer: Write the first step as a sentence: identify the base fee, included allowance, threshold and applicable extra charge. A calculator can multiply figures, but only the learner can decide which gigabytes belong above the billing threshold. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 3. Question: Under 1 GB = 1,000 MB, convert 3 GB into MB. Method: Multiply 3×1,000=3000 MB. Check: Dividing 3000 MB by 1,000 gives 3 GB. Watch for: This exercise specifies decimal units, not GiB.

Independent transfer: Estimate the resulting bill before completing it. For a subscription with positive extra charges the total should not be less than the fixed fee. If the calculation violates that basic check, look for a wrong sign, missing bracket or misread allowance. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 4. Question: Under 1 GB = 1,000 MB, convert 3.5 GB into MB. Method: Multiply 3.5×1,000=3500 MB. Check: Dividing 3500 MB by 1,000 gives 3.5 GB. Watch for: This exercise specifies decimal units, not GiB.

Independent transfer: Change the usage while keeping the plan the same. Predict whether the bill remains constant or begins to rise, then test the prediction. This reveals whether the threshold model is understood rather than memorised as one numerical answer. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Remaining included allowance

This group focuses on remaining included allowance. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 5. Question: A plan includes 10 GB and 4 GB has been used. Find unused data. Method: Subtract 10−4=6 GB remaining. Check: Used plus remaining equals the original 10 GB. Watch for: Unused quantity is not automatically a monetary refund.

Independent transfer: Check by running the calculation backwards. Subtract the fixed charge from the final total to isolate extra cost, then divide by the stated overage rate where permitted. The answer should match the chargeable data above allowance. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 6. Question: A plan includes 12 GB and 5 GB has been used. Find unused data. Method: Subtract 12−5=7 GB remaining. Check: Used plus remaining equals the original 12 GB. Watch for: Unused quantity is not automatically a monetary refund.

Independent transfer: Use an invented comparison table to make assumptions visible. Calculate plan totals for one common usage level, apply each inclusion rule separately, and explain which option is cheaper. Repeat at a different usage value to see whether the choice changes. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 7. Question: A plan includes 14 GB and 6 GB has been used. Find unused data. Method: Subtract 14−6=8 GB remaining. Check: Used plus remaining equals the original 14 GB. Watch for: Unused quantity is not automatically a monetary refund.

Independent transfer: Ask whether a result must be a whole unit. A count of complete extra billing blocks may require rounding up, while proportionally charged gigabytes need not. Only the written exercise can authorize that change to the mathematical operation. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 8. Question: A plan includes 16 GB and 7 GB has been used. Find unused data. Method: Subtract 16−7=9 GB remaining. Check: Used plus remaining equals the original 16 GB. Watch for: Unused quantity is not automatically a monetary refund.

Independent transfer: Distinguish a percentage of included allowance from an absolute quantity of gigabytes. The two describe different things. Convert the percentage back to data units and verify the value against the original usage figure. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Allowance consumption percentage

This group focuses on allowance consumption percentage. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 9. Question: A user consumes 3 GB from a 12 GB allowance. Find the percentage used. Method: Percentage=3/12×100≈25.00%. Check: Multiplying the unrounded share by 12 GB recovers 3 GB. Watch for: The denominator is included allowance, not the used quantity.

Independent transfer: After two days, attempt a new problem with changed tariff values and no worked formula. A useful correction appears when the student selects the right cost model independently and can explain why a seemingly cheaper headline fee may mislead. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 10. Question: A user consumes 4 GB from a 14 GB allowance. Find the percentage used. Method: Percentage=4/14×100≈28.57%. Check: Multiplying the unrounded share by 14 GB recovers 4 GB. Watch for: The denominator is included allowance, not the used quantity.

Independent transfer: Finish the question in the terms it actually asks for: amount of data remaining, percentage used, total bill or affordable whole increments. A final number without its unit or model interpretation is incomplete even when the arithmetic is correct. Then change one input, complete the new calculation without seeing this worked line, and explain why the result satisfies the tariff rule. The purpose is to repair the first mistaken interpretation, not merely copy an earlier bill.

Worked example 11. Question: A user consumes 5 GB from a 16 GB allowance. Find the percentage used. Method: Percentage=5/16×100≈31.25%. Check: Multiplying the unrounded share by 16 GB recovers 5 GB. Watch for: The denominator is included allowance, not the used quantity.

Worked example 12. Question: A user consumes 6 GB from a 18 GB allowance. Find the percentage used. Method: Percentage=6/18×100≈33.33%. Check: Multiplying the unrounded share by 18 GB recovers 6 GB. Watch for: The denominator is included allowance, not the used quantity.

Fixed fee plus overage

This group focuses on fixed fee plus overage. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 13. Question: A fictional plan costs $18.00 for 10 GB plus $3.00 per extra GB. Use is 13 GB. Find total. Method: Extra=3 GB; charge=$9.00. Total=$18.00+$9.00=$27.00. Check: Subtracting base from total gives the calculated extra charge. Watch for: Do not charge included GB a second time.

Worked example 14. Question: A fictional plan costs $20.00 for 10 GB plus $3.50 per extra GB. Use is 14 GB. Find total. Method: Extra=4 GB; charge=$14.00. Total=$20.00+$14.00=$34.00. Check: Subtracting base from total gives the calculated extra charge. Watch for: Do not charge included GB a second time.

Worked example 15. Question: A fictional plan costs $22.00 for 10 GB plus $4.00 per extra GB. Use is 15 GB. Find total. Method: Extra=5 GB; charge=$20.00. Total=$22.00+$20.00=$42.00. Check: Subtracting base from total gives the calculated extra charge. Watch for: Do not charge included GB a second time.

Worked example 16. Question: A fictional plan costs $24.00 for 10 GB plus $4.50 per extra GB. Use is 16 GB. Find total. Method: Extra=6 GB; charge=$27.00. Total=$24.00+$27.00=$51.00. Check: Subtracting base from total gives the calculated extra charge. Watch for: Do not charge included GB a second time.

Compare two monthly plans

This group focuses on compare two monthly plans. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 17. Question: A is $18 for 10 GB plus $2/extra GB. B is $25 for 15 GB plus $1/extra GB. At 12 GB, which is cheaper? Method: A total=$22.00; B total=$25.00. Cheaper choice: A; difference=$3.00. Check: The same 12-GB usage is used for both distinct tariffs. Watch for: Base fees alone do not settle the comparison.

Worked example 18. Question: A is $18 for 10 GB plus $2/extra GB. B is $25 for 15 GB plus $1/extra GB. At 14 GB, which is cheaper? Method: A total=$26.00; B total=$25.00. Cheaper choice: B; difference=$1.00. Check: The same 14-GB usage is used for both distinct tariffs. Watch for: Base fees alone do not settle the comparison.

Worked example 19. Question: A is $18 for 10 GB plus $2/extra GB. B is $25 for 15 GB plus $1/extra GB. At 16 GB, which is cheaper? Method: A total=$30.00; B total=$26.00. Cheaper choice: B; difference=$4.00. Check: The same 16-GB usage is used for both distinct tariffs. Watch for: Base fees alone do not settle the comparison.

Worked example 20. Question: A is $18 for 10 GB plus $2/extra GB. B is $25 for 15 GB plus $1/extra GB. At 18 GB, which is cheaper? Method: A total=$34.00; B total=$28.00. Cheaper choice: B; difference=$6.00. Check: The same 18-GB usage is used for both distinct tariffs. Watch for: Base fees alone do not settle the comparison.

Data consumption per day

This group focuses on data consumption per day. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 21. Question: An invented activity consumes 0.6 GB/day over 5 days. Find total usage. Method: Multiply 0.6×5=3 GB. Check: Dividing total by 5 days returns 0.6 GB/day. Watch for: A fixed rate is a classroom assumption, not a forecast.

Worked example 22. Question: An invented activity consumes 0.8 GB/day over 6 days. Find total usage. Method: Multiply 0.8×6=4.8 GB. Check: Dividing total by 6 days returns 0.8 GB/day. Watch for: A fixed rate is a classroom assumption, not a forecast.

Worked example 23. Question: An invented activity consumes 1 GB/day over 7 days. Find total usage. Method: Multiply 1×7=7 GB. Check: Dividing total by 7 days returns 1 GB/day. Watch for: A fixed rate is a classroom assumption, not a forecast.

Worked example 24. Question: An invented activity consumes 1.2 GB/day over 8 days. Find total usage. Method: Multiply 1.2×8=9.6 GB. Check: Dividing total by 8 days returns 1.2 GB/day. Watch for: A fixed rate is a classroom assumption, not a forecast.

Whole extra GB within a budget

This group focuses on whole extra gb within a budget. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 25. Question: A fictional plan costs $20 for 8 GB plus $2 per full extra GB. Budget is $30.00. Find maximum whole GB. Method: Extra whole GB=(30−20)/2=5; total allowance plus extra=13 GB. Check: One more extra GB would cost $32.00, above budget. Watch for: Whole-unit billing is explicitly specified in this exercise.

Worked example 26. Question: A fictional plan costs $20 for 8 GB plus $2 per full extra GB. Budget is $32.00. Find maximum whole GB. Method: Extra whole GB=(32−20)/2=6; total allowance plus extra=14 GB. Check: One more extra GB would cost $34.00, above budget. Watch for: Whole-unit billing is explicitly specified in this exercise.

Worked example 27. Question: A fictional plan costs $20 for 8 GB plus $2 per full extra GB. Budget is $34.00. Find maximum whole GB. Method: Extra whole GB=(34−20)/2=7; total allowance plus extra=15 GB. Check: One more extra GB would cost $36.00, above budget. Watch for: Whole-unit billing is explicitly specified in this exercise.

Worked example 28. Question: A fictional plan costs $20 for 8 GB plus $2 per full extra GB. Budget is $36.00. Find maximum whole GB. Method: Extra whole GB=(36−20)/2=8; total allowance plus extra=16 GB. Check: One more extra GB would cost $38.00, above budget. Watch for: Whole-unit billing is explicitly specified in this exercise.

Invented roaming day charge

This group focuses on invented roaming day charge. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 29. Question: A hypothetical no-other-fees roaming pass costs $6.00 each day for 3 days. Find total. Method: Multiply 3×$6.00=$18.00. Check: Dividing total by 3 recovers the daily fee. Watch for: This amount is not a live commercial rate.

Worked example 30. Question: A hypothetical no-other-fees roaming pass costs $8.00 each day for 4 days. Find total. Method: Multiply 4×$8.00=$32.00. Check: Dividing total by 4 recovers the daily fee. Watch for: This amount is not a live commercial rate.

Worked example 31. Question: A hypothetical no-other-fees roaming pass costs $10.00 each day for 5 days. Find total. Method: Multiply 5×$10.00=$50.00. Check: Dividing total by 5 recovers the daily fee. Watch for: This amount is not a live commercial rate.

Worked example 32. Question: A hypothetical no-other-fees roaming pass costs $12.00 each day for 6 days. Find total. Method: Multiply 6×$12.00=$72.00. Check: Dividing total by 6 recovers the daily fee. Watch for: This amount is not a live commercial rate.

Twenty-five percent usage increase

This group focuses on twenty-five percent usage increase. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 33. Question: Monthly use rises 25% from 8 GB. Calculate the new quantity. Method: New use=8×1.25=10 GB. Check: Increase=2 GB, which is 25% of 8 GB. Watch for: A percentage increase does not mean adding 25 gigabytes.

Worked example 34. Question: Monthly use rises 25% from 10 GB. Calculate the new quantity. Method: New use=10×1.25=12.5 GB. Check: Increase=2.5 GB, which is 25% of 10 GB. Watch for: A percentage increase does not mean adding 25 gigabytes.

Worked example 35. Question: Monthly use rises 25% from 12 GB. Calculate the new quantity. Method: New use=12×1.25=15 GB. Check: Increase=3 GB, which is 25% of 12 GB. Watch for: A percentage increase does not mean adding 25 gigabytes.

Worked example 36. Question: Monthly use rises 25% from 14 GB. Calculate the new quantity. Method: New use=14×1.25=17.5 GB. Check: Increase=3.5 GB, which is 25% of 14 GB. Watch for: A percentage increase does not mean adding 25 gigabytes.

Steady MB/min data rate

This group focuses on steady mb/min data rate. Read the question’s precise unit, threshold and charging assumption before calculating. The four variations are designed to make method selection easier when a new offer uses different numbers.

Worked example 37. Question: At a fictional 50 MB/min for 30 minutes, find MB and decimal GB used. Method: Total=50×30=1500 MB=1.5 GB. Check: The GB value multiplied by 1000 returns 1500 MB. Watch for: A rate is not the same as a total data quantity.

Worked example 38. Question: At a fictional 60 MB/min for 35 minutes, find MB and decimal GB used. Method: Total=60×35=2100 MB=2.1 GB. Check: The GB value multiplied by 1000 returns 2100 MB. Watch for: A rate is not the same as a total data quantity.

Worked example 39. Question: At a fictional 70 MB/min for 40 minutes, find MB and decimal GB used. Method: Total=70×40=2800 MB=2.8 GB. Check: The GB value multiplied by 1000 returns 2800 MB. Watch for: A rate is not the same as a total data quantity.

Worked example 40. Question: At a fictional 80 MB/min for 45 minutes, find MB and decimal GB used. Method: Total=80×45=3600 MB=3.6 GB. Check: The GB value multiplied by 1000 returns 3600 MB. Watch for: A rate is not the same as a total data quantity.

Six common mistakes in tariff comparisons

Treating the entire usage as extra data

Only use above the explicitly included threshold attracts overage under the stated cost model. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

Mixing GB and GiB conventions

Use the problem’s declared units and convert the quantities before comparison. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

Assuming usage cannot exceed 100% of allowance

It can; what happens commercially beyond inclusion requires separate stated rules. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

Comparing fixed charges alone

Calculate complete bills for the same use, including each plan’s extra-data terms. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

Rounding proportional data charges to whole units without authority

Use ceilings only when billing increments are explicitly defined as whole blocks. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

Inventing rollover or refund policies

Data left unused is a quantity, not necessarily an additional financial benefit. Repair the first invalid assumption, then retry a fresh plan without the model solution visible. A correct answer must fit the stated conditions and give the requested unit.

How a small-group Maths tutor can make tariffs clearer

A Secondary 3 G3 Mathematics tutor in Bukit Timah can present two different invented subscription tables and a fixed usage amount. Each student first highlights the included allowance, then computes the amount above it and the complete bill. Comparing their methods reveals whether anyone has accidentally charged included data again.

The tutor can raise usage and ask when the preferred plan changes. A later independent example with percentage usage, whole-billing increments or a budget adds another decision without changing the underlying Mathematics of ratios and inequalities.

The unchanged Clementi Secondary 1 small-group Mathematics reference provides a foundation-stage teaching example. For the current year level, consult the Secondary 3 G3 Bukit Timah Mathematics tuition overview. Actual lesson arrangements and provider terms should be checked independently.

A six-week practice route

Week 1 — convert data units

Work with explicitly defined decimal MB and GB, explaining how conversion affects numerical size. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Week 2 — identify allowance thresholds

Practise used, remaining, extra and percentage-of-allowance calculations. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Week 3 — build total-bill expressions

Separate subscription base from chargeable overage and other given costs. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Week 4 — compare two hypothetical plans

Compute complete costs at a common usage value and interpret any break-even change. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Week 5 — budget and billing-block constraints

Use inequalities and integer ceiling rules only where the exercise requires them. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Week 6 — mixed unlabelled comparisons

Use fresh tariffs, check the answer against both plan rules and explain the conclusion. Keep a dated first attempt and a later unseen variant. Progress means the learner chooses the correct rate, denominator and restriction independently.

Frequently asked questions

Does 1 GB always mean 1000 MB?

These exercises explicitly use decimal data units; real services or software may use other definitions. Use a new offer to see whether the learner can explain the method without hints.

How do I find unused data?

Subtract use from the included allowance when the stated amount remains within it. Use a new offer to see whether the learner can explain the method without hints.

Can usage percentage exceed 100?

Yes. It means the stated reference allowance was exceeded. Use a new offer to see whether the learner can explain the method without hints.

What is overage?

The portion of actual usage beyond the included allowance, under the specified billing model. Use a new offer to see whether the learner can explain the method without hints.

Why is a cheap subscription sometimes dearer?

Its overage rate or included threshold may lead to a higher complete bill. Use a new offer to see whether the learner can explain the method without hints.

Should extra GB be rounded up?

Only if the exercise says whole additional billing blocks are charged. Use a new offer to see whether the learner can explain the method without hints.

How do I set a data budget?

Build a cost inequality using fixed and variable terms, then respect the stated unit constraints. Use a new offer to see whether the learner can explain the method without hints.

Does unused data roll over?

Not automatically; the question must supply that condition. Use a new offer to see whether the learner can explain the method without hints.

Are these current Singapore operator offers?

No. They are fictional educational examples. Use a new offer to see whether the learner can explain the method without hints.

How does K310 apply here?

It teaches rates, ratios, percentages, inequalities and contextual problem solving. Use a new offer to see whether the learner can explain the method without hints.

Official course reference: 2027 K310 SEC G3 Mathematics syllabus. All practice tariffs are invented, and this article neither quotes nor endorses a telecommunications plan.

The takeaway

Did you know? A mobile bill is really a Mathematics model of a fixed fee, an allowance and a rate above a threshold. State the given conditions, choose the correct units, compare complete costs and verify the result against the original plan. The same thinking works in many other real-world budget problems.

Secondary 3 G3 Mathematics Tutor Bukit Timah | Mobile Data Plans: Unit Rates, Percentages and Bills