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Cogito

Grade 3 Math · Chapter 2 · Lesson 3

Practice Worksheet

Estimating Sums and Differences

A quick answer that tells you if the real one is sensible.

10 problems · about 12 minutes · 3.NBT.A.1, 3.OA.D.8

NameDate

Figure — use these to answer the problems

Round each number first, then add the rounded ones.
280290300halfway
The number287
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

3 problems

  1. From “Rounding to the Nearest Hundred”

    Round 649 to the nearest hundred.

    Answer

  2. From “Rounding to the Nearest Ten”

    Round 73 to the nearest ten.

    Answer

  3. From “Multiplication and Division Word Problems”

    5 boxes with 8 pens each. How many pens?

    Answer

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. Estimate 406 + 195 to the nearest hundred.

    Answer

  2. What is an estimate for?

    • Checking whether an answer is sensible.
    • Replacing the exact answer.

  3. Estimate 312 + 289 to the nearest hundred.

    Answer

Build It Up

The same ideas with more to keep track of.

1 problem

  1. Estimate 587 − 291 to the nearest hundred.

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

3 problems

  1. Estimate 48 + 33 to the nearest ten.

    Answer

  2. Two Crowds

    178 and 216 people. Estimate the total to the nearest hundred.

    Answerpeople

  3. Checking a Friend

    Leo says 412 − 189 = 623. Estimate to check: 400 − 200 is what?

    Answer