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SUBTRACTION ESTIMATION

Estimate differences quickly to check your work and catch mistakes.

L4L5

CS.N.3.3·Estimating results of calculations with natural numbers(III)

Section 1 / 3

ESTIMATING DIFFERENCES

Round both numbers to the nearest ten or hundred, then subtract. This gives you a quick ballpark answer you can use to check your exact calculation.

Estimate 74 − 38

1Round: 70 − 40 = 30

2Exact: 74 − 38 = 36

3Close estimate!

= 36

LEADER TIP

Pair estimation with exact calculation so students learn to self-check. When answers are far from estimates, alarm bells should ring.

BEFORE THIS LESSON, TRY

PRACTICE WITH THESE GAMES

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