3B · Chapter 15 · Lesson 4
Subtracting Money
Subtract money amounts with regrouping across dollars and cents.
Today's mathematical question
You have $6.11 and spend $1.21. How much remains?
Learning target
Subtract money amounts with regrouping across dollars and cents.
Before starting: Prior lesson: Adding Money. Try the warm-up independently.
Prerequisite · 3 questions
Check earlier skills first
These are earlier ideas you need for today; revisit them if they are difficult.
- P1
A notebook costs $5.38 and a pencil case costs $3.51. What is the total cost?
Reveal explanation
Answer: $8.89
Add cents: 538 + 351 = 889 cents = $8.89.
- P2
A notebook costs $8.43 and a pencil case costs $1.64. What is the total cost?
Reveal explanation
Answer: $10.07
Add cents: 843 + 164 = 1007 cents = $10.07.
- P3
A notebook costs $2.61 and a pencil case costs $2.88. What is the total cost?
Reveal explanation
Answer: $5.49
Add cents: 261 + 288 = 549 cents = $5.49.
Learn and understand
To subtract money when there are too few cents, exchange one dollar for 100 cents. For $5.10 minus $2.75, rename $5.10 as $4 and 110 cents, subtract the cents and then dollars. The difference is $2.35. Subtract $2.85 from $5.10 by exchanging one dollar for 100 cents, or convert both to cents first. Either route gives $2.25.
Represent it three ways
- Concrete: Build equal pieces, measures, counters or shapes with real objects when useful.
- Pictorial: Show a before-and-after place-value chart with a one-dollar exchange. Check by adding the difference to the amount spent.
- Abstract: Write the matching number sentence, calculation, comparison or mathematical description. Explain each number's unit.
Important vocabulary
- difference
- result of subtraction
- regroup
- exchange equal-value units
- change
- amount of money remaining
Fully worked examples and checks
Try each new understanding check before revealing the explanation.
Worked example 1
Explore, calculate, verify
You have $6.11 and spend $1.21. How much remains?
- Identify the whole, the units, and what the question asks.
- Subtract 121 cents from 611 cents. The 490 cents remaining equal $4.90.
- Check that the answer uses the right units and makes sense.
Answer: $4.90
Check your understanding 1
You have $2.18 and spend $0.88. How much remains?
Reveal answer and explanation
$1.30 — Subtract 88 cents from 218 cents. The 130 cents remaining equal $1.30.
Worked example 2
Explore, calculate, verify
You have $3.38 and spend $2.14. How much remains?
- Identify the whole, the units, and what the question asks.
- Subtract 214 cents from 338 cents. The 124 cents remaining equal $1.24.
- Check that the answer uses the right units and makes sense.
Answer: $1.24
Check your understanding 2
You have $9.38 and spend $0.96. How much remains?
Reveal answer and explanation
$8.42 — Subtract 96 cents from 938 cents. The 842 cents remaining equal $8.42.
Worked example 3
Explore, calculate, verify
You have $6.90 and spend $2.35. How much remains?
- Identify the whole, the units, and what the question asks.
- Subtract 235 cents from 690 cents. The 455 cents remaining equal $4.55.
- Check that the answer uses the right units and makes sense.
Answer: $4.55
Check your understanding 3
You have $11.35 and spend $3.80. How much remains?
Reveal answer and explanation
$7.55 — Subtract 380 cents from 1135 cents. The 755 cents remaining equal $7.55.
Guided · 5 questions
Guided practice
Keep the model and earlier examples visible while practising.
- G1
You have $4.93 and spend $1.65. How much remains?
Reveal explanation
Answer: $3.28
Subtract 165 cents from 493 cents. The 328 cents remaining equal $3.28.
- G2
You have $8.82 and spend $0.71. How much remains?
Reveal explanation
Answer: $8.11
Subtract 71 cents from 882 cents. The 811 cents remaining equal $8.11.
- G3
You have $8.43 and spend $2.38. How much remains?
Reveal explanation
Answer: $6.05
Subtract 238 cents from 843 cents. The 605 cents remaining equal $6.05.
- G4
You have $9.17 and spend $3.60. How much remains?
Reveal explanation
Answer: $5.57
Subtract 360 cents from 917 cents. The 557 cents remaining equal $5.57.
- G5
You have $5.31 and spend $1.34. How much remains?
Reveal explanation
Answer: $3.97
Subtract 134 cents from 531 cents. The 397 cents remaining equal $3.97.
Independent · 8 questions
Independent practice
Work these without hints and explain the method used. Write answers on paper.
- I1
You have $8.09 and spend $2.73. How much remains?
Reveal explanation
Answer: $5.36
Subtract 273 cents from 809 cents. The 536 cents remaining equal $5.36.
- I2
You have $5.41 and spend $2.49. How much remains?
Reveal explanation
Answer: $2.92
Subtract 249 cents from 541 cents. The 292 cents remaining equal $2.92.
- I3
You have $7.84 and spend $2.14. How much remains?
Reveal explanation
Answer: $5.70
Subtract 214 cents from 784 cents. The 570 cents remaining equal $5.70.
- I4
You have $10.74 and spend $2.12. How much remains?
Reveal explanation
Answer: $8.62
Subtract 212 cents from 1074 cents. The 862 cents remaining equal $8.62.
- I5
You have $5.10 and spend $1.32. How much remains?
Reveal explanation
Answer: $3.78
Subtract 132 cents from 510 cents. The 378 cents remaining equal $3.78.
- I6
You have $6.92 and spend $1.57. How much remains?
Reveal explanation
Answer: $5.35
Subtract 157 cents from 692 cents. The 535 cents remaining equal $5.35.
- I7
You have $10.82 and spend $2.87. How much remains?
Reveal explanation
Answer: $7.95
Subtract 287 cents from 1082 cents. The 795 cents remaining equal $7.95.
- I8
You have $5.47 and spend $1.87. How much remains?
Reveal explanation
Answer: $3.60
Subtract 187 cents from 547 cents. The 360 cents remaining equal $3.60.
Challenge · 2 questions
Challenge and error analysis
Go beyond arithmetic: justify a claim, correct reasoning, or connect two representations.
- C1
Explain why $6.05 is 6 dollars and 5 cents rather than 6 dollars and 50 cents.
Reveal explanation
Answer: $6.05
The first digit after the decimal is tens of cents, and the second is ones of cents.
- C2
You have $10.00 and spend $6.75. Find the change by counting up, explaining each jump.
Reveal explanation
Answer: $3.25
Count 25 cents to $7.00, then $3.00 more to $10.00, for $3.25 change.
Exit · 3 questions
Exit check
Solve independently, then return on another day to check retention.
- E1
You have $9.69 and spend $3.28. How much remains?
Reveal explanation
Answer: $6.41
Subtract 328 cents from 969 cents. The 641 cents remaining equal $6.41.
- E2
You have $6.59 and spend $1.80. How much remains?
Reveal explanation
Answer: $4.79
Subtract 180 cents from 659 cents. The 479 cents remaining equal $4.79.
- E3
You have $9.68 and spend $2.02. How much remains?
Reveal explanation
Answer: $7.66
Subtract 202 cents from 968 cents. The 766 cents remaining equal $7.66.