Chapter 9 of 11All chapters
Chapter 9 of 11
Division
Factor the divisor into easy steps.
Divide in stages
To divide by 12, halve twice then divide by 3, or divide by 3 then halve twice. Splitting the divisor into small factors turns one hard step into two easy ones.
- 144 divided by 12 is the twelve times table, so recall beats calculation.
- Dividing by 5 is doubling and moving the decimal point.
Divisibility tests
A number divides by 3 if its digits sum to a multiple of 3, by 9 if they sum to a multiple of 9, and by 4 if the last two digits do. These catch factors quickly.