Round and adjust: adding and subtracting worksheets

Adding 99 is adding 100 and taking one back. These free printable worksheets practise that move — the compensation strategy — for numbers just under and just over a hundred, in both addition and subtraction, for grades 3 and 4.

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Round and adjust: adding and subtracting

$Round and adjust: adding and subtracting worksheet — ± 99, 98, 199, 101, free printable with answer key$

The answer key prints on a separate page.

What's on this sheet

253 + 298 becomes 253 + 300 − 2: add the round number, which is easy, then pay back the 2 that was borrowed. The answer is 553 − 2 = 551, reached without a single carry. The same works for 199, 399 and 101, where the adjustment goes the other way.

Why this sheet works

Subtraction is where the strategy teaches something new. 503 − 198 becomes 503 − 200 + 2, and the adjustment is ADDED: taking away 200 took away 2 too many, so they are given back. Children who get this wrong almost always subtract the 2 as well, and the answer key shows exactly where.

How this one works

676 − 98

676 − 98=676 − 100 + 2

676 − 100 + 2=576 + 2

576 + 2=578

Take away the round number instead, then adjust. Taking away too much means adding some back.
Work out the easy part first: 676 − 100 + 2 = 576 + 2.
Then finish: 576 + 2 = 578.

Mental mathRound and adjust (+ −)

Name: Date:

Use the round number, then adjust.

1676 − 98= 676 − 100 + 2= + 2=

298 + 99= 100 + 100 − 2 − 1= − =

3725 + 299= 725 + 300 − 1= − 1=

499 + 197= 100 + 200 − 1 − 3= − =

5721 − 99= 721 − 100 + 1= + 1=

6534 − 98= 534 − 100 + 2= + 2=

7298 + 399= 300 + 400 − 2 − 1= − =

8699 + 198= 699 + 200 − 2= − 2=

9621 + 99= 621 + 100 − 1= − 1=

10715 − 102= 715 − 100 − 2= − 2=

11576 + 98= 576 + 100 − 2= − 2=

1298 + 499= 100 + 500 − 2 − 1= − =

Mental math · Round and adjust (+ −)Answer key

1. 676 − 98 = 676 − 100 + 2 = 576 + 2 = 5782. 98 + 99 = 100 + 100 − 2 − 1 = 200 − 3 = 1973. 725 + 299 = 725 + 300 − 1 = 1025 − 1 = 10244. 99 + 197 = 100 + 200 − 1 − 3 = 300 − 4 = 2965. 721 − 99 = 721 − 100 + 1 = 621 + 1 = 6226. 534 − 98 = 534 − 100 + 2 = 434 + 2 = 4367. 298 + 399 = 300 + 400 − 2 − 1 = 700 − 3 = 6978. 699 + 198 = 699 + 200 − 2 = 899 − 2 = 8979. 621 + 99 = 621 + 100 − 1 = 721 − 1 = 72010. 715 − 102 = 715 − 100 − 2 = 615 − 2 = 61311. 576 + 98 = 576 + 100 − 2 = 676 − 2 = 67412. 98 + 499 = 100 + 500 − 2 − 1 = 600 − 3 = 597

Round and adjust: adding and subtracting worksheets

What's on this sheet

How this one works

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