Times table fluency
Lesson 5 of 10
Doubling to build tables
Objective. Derive the 4 and 8 times tables from the 2 times table.
The key idea
Doubling twice multiplies by 4; doubling three times multiplies by 8. So 7 × 8 is 7 doubled to 14, to 28, to 56.
Worked example
Work out 7 × 8 by doubling.
- 17 × 2 = 14.
- 214 × 2 = 28 (that is 7 × 4).
- 328 × 2 = 56 (that is 7 × 8).
Answer: 56
Practice
Each question comes with a picture and a listen button. Try it first, then reveal the answer.
Common mistake. Doubling only twice when multiplying by 8.
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