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Shift for 10, 100 and 1,000: a mental math trick

When to use it: Multiplying or dividing by 10, 100 or 1,000.

Worked example

3.2 × 100 on a place-value chartThe digits of 3.2 slide two places left past the fixed decimal point and read 320.hundredstensonestenths320× 1003.2 × 100 = 320
  1. Times 10 moves every digit one place to the left: 45 becomes 450.
  2. Dividing by 10 moves every digit one place to the right: 45 becomes 4.5.
  3. Count the zeros to know how many places to move.

example 3.2 × 100

  1. 100 has two zeros, so move two places left.
  2. 3.2 becomes 320.

Answer: 320

Try three

  1. 5,528 ÷ 1,000

    Show the answer

    5.528

  2. 1,897 ÷ 1,000

    Show the answer

    1.897

  3. 68.7 × 10

    Show the answer

    687

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Used in: Gaps & place value · Division · Decimals

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This technique and its worked example are Doing Math’s own lesson text, checked by a blind re-solve and a review on September 27, 2026.