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Mental maths · lesson 10 of 28 · free

Multiply by 4 and 8 by doubling — Mental Maths Mastery

4 is 2 × 2 and 8 is 2 × 2 × 2. So you never need the 4 or 8 table for big numbers — just keep doubling.

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How to do it in your head

Double, double, double — “× 4 is two doubles, × 8 is three”

  1. × 2: double once.
  2. × 4: double, then double again.
  3. × 8: double three times.

Use it for: Packs of 4 or 8, legs of animals, and bigger sums like 35 × 8.

Worked example: 23 × 8 = 184

  1. Double 23: 46.
  2. Double again: 92.
  3. Double once more: 184.

Check: 23 × 8 = 20 × 8 + 3 × 8 = 160 + 24 = 184 ✓

▶ Watch it animated

✓ 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 10 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 🐙 Octo Doubler badge when you pass — and a certificate when you finish all 6 lessons of Part 2 · Mental multiplication & division. You can still take the test without signing in.

🖨️ Multiply by 4 and 8 Mental Maths Worksheet

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