Multiplying decimals by whole numbers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Multiplying decimals by whole numbers

Mathematics · Multiplication & Division · ages 10-11
Name ______________________   Date ____________

  1. What is 2.5 x 4?

    Answer: ______________

  2. What is 3.2 x 5?

    • 1.6
    • 16
    • 15
    • 8.2

  3. Look at 3.47. How many digits come after the decimal point?

    3.47
    • 1
    • 2
    • 3

  4. 5.62 has 2 digits after the decimal point, so the answer to 5.62 × 3 will also have 2 digits after the point.

    5.62

    Circle one:   True   False

  5. What is 1.25 x 8?

    Answer: ______________

  6. Which expanded form matches 4.3 × 2?

    • (4 × 2) + (0.3 × 2)
    • (4 × 2) + (3 × 2)
    • (4 + 0.3) + 2

  7. What is 4.56 x 7?

    • 3.192
    • 28.92
    • 31.92
    • 319.2

  8. Mia multiplies 2.4 x 3 and writes 6.12 because she multiplied 2 x 3 and 4 x 3 separately. Is Mia right?

    Circle one:   True   False

  9. Zara multiplied 2.15 × 4 and wrote the answer 860. What did she forget to do?

    • Multiply the ones digit
    • Add a zero at the end
    • Move the point back in

  10. Which reasoning explains why 3.2 x 5 = 16.0?

    • 16.0 is correct: 32 tenths x 5 = 160 tenths = 16.0
    • The decimal point vanishes when multiplying
    • Whole numbers absorb decimals
    • 5 x 3.2 rounds to 5 x 3
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Answer key

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Multiplying decimals by whole numbers W1-mt_SoDP1fSQEB-s1

  1. 10 · The answer is 10 because 25 tenths times 4 is 100 tenths, which is 10.
  2. 16 · 16 is correct because 32 tenths times 5 is 160 tenths, which is 16.0.
  3. 2 · The digits after the point are 4 and 7, so there are 2.
  4. True · The number of decimal digits in the answer always matches the number in the decimal you started with.
  5. 10 · The answer is 10 because 125 hundredths times 8 is 1,000 hundredths, which is 10.
  6. (4 × 2) + (0.3 × 2) · 4.3 splits into 4 and 0.3, so each part gets multiplied by 2 separately: 8 + 0.6 = 8.6.
  7. 31.92 · 31.92 is correct because 456 times 7 = 3,192 with two decimal places restored.
  8. False · Mia is wrong. Her split gives 6 + 1.2 = 7.2, not 6.12: she glued the parts instead of adding them.
  9. Move the point back in · 215 × 4 = 860 is correct, but 2.15 has 2 decimal digits, so the point needs to go back in: 8.60.
  10. 16.0 is correct: 32 tenths x 5 = 160 tenths = 16.0 · 32 tenths x 5 = 160 tenths = 16.0 explains it with exact place value.
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