Multiplying and dividing in your head

Use facts you know for bigger numbers.

Crates of bananas

A trader has 30 crates with 4 bunches in each. How many bunches? Use 3 × 4 = 12, so 30 × 4 = 120.

When we multiply by 10, each digit moves one place to the left. A zero holds the ones place. × 100 moves digits two places: 23 × 100 = 2300.

If you know 6 × 4 = 24, then 60 × 4 = 240. And 240 ÷ 4 = 60. These are related facts.

Not all numbers divide exactly. 14 ÷ 4 = 3 with 2 left over. We write 14 ÷ 4 = 3 r 2. The 2 is the remainder.

When you multiply three numbers, group any two first. 2 × 5 = 10, then 10 × 7 = 70. This is the associative property – it makes multiplying quicker.