Making 10
To add a small number, first fill up to the next ten, then add what is left.
8 + 5 = 13
- 8 + 2 = 10
- 10 + 3 = 13
Mental math techniques
Tricks to calculate faster in your head, sorted by level. Each one comes with a worked example, step by step.
Level 1 · Easy 3 techniques
Adding or taking away 9
9 is 10 − 1: add (or take away) 10, then fix it by 1. It works with 19, 29… too.
47 + 9 = 56
- 47 + 10 = 57
- 57 − 1 = 56
Near doubles
Two neighbouring numbers: start from the double you know, then add the gap.
7 + 8 = 15
- 7 + 7 = 14
- 14 + 1 = 15