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Tables & multiplication · lesson 14 of 22 · free

Doubling and halving — Tables & Multiplication Mastery

If you double one number and halve the other, the answer does not change. Use it to turn a number ending in 5 into a round number.

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How it works

Double and halve — “double one number, halve the other — the answer stays the same”

  1. Find the number ending in 5 and the even number.
  2. Double the one ending in 5; halve the even one.
  3. Repeat while it helps (25 → 50 → 100), then multiply.

Use it for: Any number ending in 5 times an even number: 35 × 16, 45 × 12, 125 × 8.

Worked example: 25 × 28 = 700

  1. Double 25 → 50, halve 28 → 14: 50 × 14.
  2. Double 50 → 100, halve 14 → 7: 100 × 7.
  3. 100 × 7 = 700.

Check: 25 × 28 = 25 × 4 × 7 = 100 × 7 = 700 ✓

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✓ Written and checked by the TalentJR team · Updated 13 Oct 2026 · How we make our lessons

✏️ Practice

Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.

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🏁 Lesson 14 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.

🏅 Sign in with Google to earn the ⚡ Doubling Dynamo badge when you pass — and a certificate when you finish all 9 lessons of Module 3 · Multiplication strategies. You can still take the test without signing in.

🖨️ Doubling and Halving Worksheet

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