How to add 9 or 8 in your head

For ages 5 to 8 (Years 1 to 3) · 2-minute read · free worksheet

Adding 9 or 8 trips up lots of children because they count on one at a time. Adding 10 is easy, so we add 10 and adjust.

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Worksheet includes an answer key for grown-ups

How it works

  1. Pretend the 9 is a 10 (or the 8 is a 10).
  2. Add 10.
  3. Take back the 1 (or 2) you borrowed.

Worked example

7 + 8: 7 + 10 = 17. We borrowed 2, so take 2 away: 15.

Top tip

It works for bigger numbers too: 34 + 19 = 34 + 20 − 1 = 53.
How to add 9 or 8 in your head: 7 + 8 = ? 7 + 10 = 17, take 2 away = 15

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