Multiplying & dividing fractions & decimals
Multiplying & dividing unit fractions
A unit fraction has a numerator of 1 (like 1/5). You can multiply one by a whole number, or divide one by a whole number.
The two ideas
• Multiplying a unit fraction by a whole number: it is repeated addition, so 1/5 × 4 = 4/5. • Dividing a unit fraction by a whole number: the pieces get smaller, so 1/2 ÷ 3 = 1/6.
Worked examples
Multiplying
- Work out 1/5 × 4.
- That is 1/5 + 1/5 + 1/5 + 1/5.
- Four fifths.
Answer: 1/5 × 4 = 4/5
Dividing
- Work out 1/2 ÷ 3.
- Split one half into 3 equal parts.
- Each part is one sixth.
Answer: 1/2 ÷ 3 = 1/6
Where you see this in real life
- Four friends each eat 1/5 of a pizza — together that's 4/5.
- Sharing half a bottle of juice equally between three glasses.
- Splitting a quarter of a cake between two people.
Key words
- Unit fraction
- A fraction with a numerator of 1, for example 1/2 or 1/5.
- Numerator
- The top number of a fraction.
- Denominator
- The bottom number of a fraction.