Fractions, Decimals and Percentages: A Guide for the 11+ Maths Exam

Three Ways of Saying the Same Thing

Here is the single most important idea your child needs to grasp: fractions, decimals and percentages are not three different topics. They are three different ways of writing exactly the same value.

A glass that is half full can be described as 1/2, as 0.5, or as 50% — and all three statements mean precisely the same thing. A battery icon showing a quarter charge is telling you 1/4, or 0.25, or 25%. Children see these representations every day without realising it: on phone screens, in shop sales, in sports statistics, and on food packaging.

Once a child truly understands this equivalence, 11+ questions on the topic stop being frightening. Whenever they see any fraction, decimal or percentage, they know they can express it in two other ways — and choose whichever form makes the question easiest to answer.

Did you know? Fraction, decimal and percentage conversion appears in virtually every 11+ maths paper, whether GL, CEM or an independent school exam. It is one of the highest-value topics your child can master, because it also unlocks harder questions on ratio, proportion and problem solving.

The Conversion Methods

The good news is that there are only a handful of methods to learn, and each one is a single step.

Worked Examples

Example 1: Convert 4/8 to a decimal and a percentage

Divide the numerator by the denominator: 4 ÷ 8 = 0.5 (five tenths). To turn the decimal into a percentage, multiply by 100: 0.5 × 100 = 50%.

So 4/8 = 0.5 = 50% — and a sharp-eyed child will also notice that 4/8 simplifies to 1/2, which they should already know equals 50%.

Example 2: Convert 25/100 to a decimal and a percentage

Divide 25 by 100 to get 0.25 (twenty-five hundredths). This tells you that 25/100 is 0.25 of the whole number one. Multiply by 100 to find the percentage: 0.25 × 100 = 25%.

Example 3: Convert 4/5 to a percentage

Divide 4 by 5 to get 0.8, then multiply by 100: 4/5 = 80%.

Tip: Ask your child to say the conversion out loud as they work: “four divided by five is nought point eight, times one hundred is eighty per cent.” Verbalising the steps builds a reliable routine they can fall back on under exam pressure.

Equivalents Worth Memorising

While your child should always be able to work a conversion out from scratch, the 11+ rewards speed. These equivalents come up so often that they are worth committing to memory:

• 1/2 = 0.5 = 50%
• 1/4 = 0.25 = 25%
• 3/4 = 0.75 = 75%
• 1/10 = 0.1 = 10%
• 1/5 = 0.2 = 20%
• 1/8 = 0.125 = 12.5%
• 1/3 ≈ 0.33 ≈ 33%

Flash cards, a poster on the bedroom wall, or a quick-fire quiz in the car all work well. The goal is instant recall — no working out required.

Spot Them in Everyday Life

Because fractions, decimals and percentages are everywhere, everyday life is a free practice resource:

• Shopping — “This jumper is 25% off. What fraction is that? What would it cost?”
• Cooking — “We need half of this 400g pack. How much is that as a decimal of a kilogram?”
• Screens and batteries — “Your tablet says 75%. What fraction of the charge is left?”
• Fundraising — “We’ve raised £250 of our £1,000 target. What percentage is that?”

A child who converts between formats casually in conversation will find exam questions on the same skill straightforward. This kind of little-and-often reinforcement is exactly the approach we recommend in our guide on how to improve your child’s 11+ maths score.

How the 11+ Tests This Topic

Exam boards rarely ask a bare “convert this” question. More often, the skill is embedded in problems such as:

• Ordering — “Put 0.4, 3/8, 45% and 1/2 in ascending order.” (Convert everything to the same format first — decimals are usually easiest.)
• Percentage of an amount — “Find 25% of £60.” (Recognise 25% as 1/4, then divide by 4.)
• Fractions of quantities — “3/5 of the 30 children in a class are girls. How many is that?”
• Worded problems — multi-step questions where converting to a friendlier format is the key that unlocks the answer.

You can see how these appear alongside other question types in our walkthrough of 11+ maths test questions and answers, and the same convert-first thinking helps with related topics such as finding the average.

Tip: When ordering mixed formats, teach your child to convert everything to decimals. Decimals line up neatly on a number line, which makes comparing them far less error-prone than juggling fractions with different denominators.

A Simple Weekly Practice Plan

Consistency beats cramming. A month of short sessions like this will do more than a single marathon revision day — a principle that applies across the whole exam, as we explain in our practical 11+ guide.

Practise Fractions, Decimals and Percentages with Our Apps

Understanding the method is the first step; fluency comes from structured practice with instant feedback.

Our 11+ Maths Learn & Test app is the ideal place to build the foundations. It offers 1,280 questions across 32 topics — including fractions, decimals and percentages — each backed by detailed study notes, so your child can review the method before testing themselves and revisit the explanation whenever they slip up.

Once the individual skills are secure, the 11+ Maths Practice Papers app puts them to work under exam conditions, with 1,200 questions across 24 full practice papers covering all 11+ maths topics, each with detailed explanations. This is where children learn to spot a hidden conversion inside a worded problem — exactly the skill the real exam demands.

Together with our verbal reasoning, non-verbal reasoning, English and vocabulary apps, the full suite offers over 8,100 questions across 7 apps, giving your child comprehensive coverage of every 11+ subject. Master the idea that 1/2, 0.5 and 50% are one and the same, practise the conversions little and often, and this high-frequency topic will become a reliable source of marks on exam day.