Home › Guides › Fractions, decimals and percentages for the 11+

Fractions, decimals and percentages for the 11+

Updated 2026-11-14

Fractions, decimals and percentages turn up in almost every 11+ maths paper, often hidden inside a word problem. The good news is that they are three ways of writing the same idea, and a few facts make them much easier.

Three ways to say the same amount

A half, 0.5 and 50% are the same amount written in three ways. Children who can move easily between the three forms find many questions quicker, because they can pick whichever form makes the sum simplest.

It helps to know these equivalents by heart:

1/2 = 0.5 = 50%
1/4 = 0.25 = 25% and 3/4 = 0.75 = 75%
1/5 = 0.2 = 20% and 1/10 = 0.1 = 10%
1/8 = 0.125 = 12.5%
1/3 is about 0.333, or 33⅓%

Fraction bars showing 1/2 = 0.5 = 50%, 1/4 = 0.25 = 25%, 3/4 = 0.75 = 75%, 1/5 = 0.2 = 20% and 1/10 = 0.1 = 10%. — The same amount written as a fraction, a decimal and a percentage.

Quick methods worth practising

Finding 10%: divide by 10. Then 5% is half of that, and 20% is double it. For example, 15% of 60 is 6 + 3 = 9.
Finding a fraction of an amount: divide by the bottom number, multiply by the top. 3/5 of 40 is 40 ÷ 5 × 3 = 24.
Comparing fractions: turn them into decimals or give them the same denominator. Which is bigger, 3/5 or 5/8? 0.6 against 0.625, so 5/8.
Simplifying: divide the top and bottom by the same number. 12/18 becomes 2/3 when you divide both by 6.

The mistakes children make most often

Thinking a bigger denominator means a bigger fraction. 1/8 is smaller than 1/6, because the whole is cut into more pieces.
Adding fractions by adding the tops and the bottoms. 1/2 + 1/4 is 3/4, not 2/6.
Lining up decimals by the last digit instead of the decimal point when adding or subtracting.
Forgetting what the question asks for: the percentage that is left, or the percentage that was taken away.

A five-minute routine

Little and often works best. Two or three times a week, ask five quick questions: one equivalent, one percentage of an amount, one fraction of an amount, one comparison and one short word problem. Mark them together and talk about any method that went wrong.

Pizza, cake and money are useful at home. Ask what fraction of the pizza is left, or what a 20% discount would take off a price in a shop.

Questions parents ask

Which year are fractions, decimals and percentages taught?

They build up through Key Stage 2. Most of what the 11+ asks for is taught by the end of Year 5, with some extension work in Year 6, so check the topics with your child's school if you are unsure.

Are calculators allowed in the 11+?

No calculator is allowed in the 11+ tests we know of, so mental and written methods matter. Check the rules for your child's test.

What should my child learn by heart?

The common equivalents (halves, quarters, fifths, tenths and eighths) and how to find 10% and 1% of an amount. Most other questions build on these.

Want to see what a paper set out like your child's test looks like? Every pack and handbook has a free sample. Find your test area or try the free flash cards.