Unitary fractions of amounts
Unitary fractions of amounts help us work out equal parts of a quantity, such as finding one third of 24 sweets or one fifth of £15. This is useful in real life whenever we share, split, or compare amounts fairly. Jump to the questions
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Topic guide
What this worksheet practises
This worksheet provides practice on finding simple "unitary" fractions of an amount. A unitary fraction is any fraction where the top number (the numerator) is exactly 1, such as 1/2, 1/5, or 1/10. This is a foundational arithmetic skill.
Key method
Because the top number is 1, this is a single-step calculation.
- Look at the fraction you are given (e.g. 1/4).
- Look at the bottom number (the denominator). This tells you how many equal pieces the total amount needs to be split into.
- Take your total amount and divide it by the bottom number.
- Because the top number is just 1, you only need one of these pieces, so your division calculation gives you the final answer immediately.
Worked example
Find 1/5 of £40.
Step 1: Look at the fraction. The bottom number is 5.
Step 2: Take the total amount (£40) and divide it by 5.
40 ÷ 5 = 8.
The answer is £8.
Common mistakes to avoid
A common mistake is multiplying the amount by the denominator instead of dividing. A student asked to find 1/4 of 12 might quickly calculate 12 × 4 = 48. Always remember: a fraction of an amount means you are taking a "piece" of it, so the final answer must be smaller than the number you started with (unless it's an improper top-heavy fraction!).
Things to remember
You can use simple known facts to speed things up. Finding 1/2 means dividing by 2 (halving). Finding 1/4 means dividing by 4 (halving and halving again). Finding 1/10 means dividing by 10 (shifting the decimal point one place to the left). Memorising these shortcuts makes mental arithmetic much faster.