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Cogito

Grade 5 Math · Chapter 3 · Lesson 3

Practice Worksheet

Estimating with Decimals

Round to the nearest whole one first.

10 problems · about 14 minutes · 5.NBT.B.7, 5.NBT.A.4

NameDate

Figure — use these to answer the problems

Rounding is nearness. The midpoint decides which way it goes.
0102030405060708090100halfway

48

The number48
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

2 problems

  1. From “Subtracting Decimals”

    1 − 0.28, in hundredths?

    Answer

  2. From “Lining Up the Places”

    0.6 + 0.27, in hundredths?

    Answer

Warm Up

Straightforward practice. Get the method working first.

4 problems

  1. Estimate 7.8 + 2.1 to the nearest whole numbers.

    Answer

  2. An answer of 0.8 to 4.5 + 3.2. Is it sensible?

    • No. It should be near 8.
    • Yes.

  3. Estimate 3.7 + 5.2 to the nearest whole numbers.

    Answer

  4. Estimate 12.1 − 4.9 to the nearest whole numbers.

    Answer

Build It Up

The same ideas with more to keep track of.

2 problems

  1. Estimate 8.45 + 2.6 to the nearest whole numbers.

    Answer

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

    • A decimal point in the wrong place.
    • An answer out by one hundredth.

Stretch Yourself

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

2 problems

  1. A Rough Answer

    Estimate 6.9 + 4.2 by rounding each to the nearest whole number.

    Answer

  2. The Difference

    Estimate 9.8 − 3.1 by rounding each to the nearest whole number.

    Answer