Multiplying fractions
You learn to multiply fractions by each other, and a fraction by a whole number.
How to work it out
- Multiply the top numbers.
- Multiply the bottom numbers.
- Simplify the resulting fraction.
A worked example
12 × 13
- Multiply the tops: 1 × 1 = 1.
- Multiply the bottoms: 2 × 3 = 6.
- It is 16.
More examples
23 × 14
- Multiply the tops: 2 × 1 = 2.
- Multiply the bottoms: 3 × 4 = 12, so 212.
- Simplify it: it is 16.
25 × 4
- Multiply only the top by 4: 2 × 4 = 8.
- Keep the 5 at the bottom.
- It is 85.
Watch out
With a whole number, you multiply the bottom too: 25 × 4 becomes 820.
A whole number like 4 is 41. The bottom is multiplied by 1, so the 5 stays.
You make the numbers below the line equal first, as you do when adding.
When multiplying you do not need to. Just multiply top by top and bottom by bottom.
Tips
- Write a whole number as a fraction with a 1 below the line: 4 is 41.
Why it works
12 × 13 means: half of a third. That piece is smaller, because you split a piece again. That is why you multiply the numbers below the line together, and the numbers above the line too.