Note the shape that disappears, then estimate the number to 1 significant figure e.g.

1. Note the shape that disappears, then estimate the number to 1 significant figure e.g. 123 rounds to 100 57.1 rounds to 60 etc

2. 128 275 18.3 37.2 4.5 3999 19.9 1280

3. 128 275 18.3 4.5 3999 19.9 1280

4. 128 275 18.3 4.5 19.9 1280

5. 128 18.3 4.5 19.9 1280

6. 128 18.3 19.9 1280

7. 128 18.3 19.9

8. 18.3 19.9

9. 18.3

11. The answers

12. 37.2 – 40 • 3999 – 4000 • 275 – 300 • 4.5 – 5 • 1280 – 1000 • 128 – 100 • 19.9 – 20 • 18.3 - 20