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Cogito

Grade 4 Math · Chapter 2 · Lesson 5

Practice Worksheet

Estimating Products

Round first, so a wrong answer stands out.

10 problems · about 13 minutes · 4.NBT.B.5, 4.OA.A.3

NameDate

Figure — use these to answer the problems

Estimate first, then work it out exactly and compare.
302
408
  • 30 × 401200
  • 2 × 4080
  • 30 × 8240
  • 2 × 816
  • 32 × 481536
First number32
Second number48
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

3 problems

  1. From “Two-Digit by Two-Digit”

    24 × 13 = ?

    Answer

  2. From “The Area Model and Partial Products”

    42 × 8 = ?

    Answer

  3. From “Multiplying by 10, 100, and 1,000”

    8 × 700 = ?

    Answer

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. Estimate 38 × 21 to the nearest ten.

    Answer

  2. What kind of mistake does an estimate catch best?

    • An answer that is wildly the wrong size.
    • An answer that is out by one.

  3. Estimate 19 × 31 to the nearest ten.

    Answer

Build It Up

The same ideas with more to keep track of.

1 problem

  1. Estimate 58 × 22 to the nearest ten.

    Answer

Stretch Yourself

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

3 problems

  1. Estimate 7 × 68 to the nearest ten.

    Answer

  2. A Rough Answer

    Estimate 41 × 29 by rounding both to the nearest ten.

    Answer

  3. The Exact One

    Now work out 41 × 29 exactly.

    Answer