Fractions, decimals and percentages are three ways of saying the same thing, and the 11+ tests whether a child can switch between them smoothly under time pressure. In today's GL Assessment papers — now the dominant format across most regions since CEM's separate tests were phased out around 2022 to 2023 — this trio shows up again and again, dressed as shopping problems, "share of an amount" questions and quick conversions. The good news is that once the core equivalents are memorised, most of these questions become fast, one-step wins. Here's a clean, confidence-building way to teach the whole topic.
Why this topic matters so much in the 11+
Fractions, decimals and percentages (often shortened to FDP) sit at the heart of the maths syllabus because so many other topics lean on them: ratio, proportion, money, and data interpretation all assume a child can convert quickly. In a typical GL paper you might face 50 questions in 50 minutes — roughly a minute each, multiple-choice with answers A to E on a separate OMR sheet, and no calculator. FDP questions are meant to be the quick ones. A child who has to work out that a half is 50% from scratch every time will bleed away seconds they need for the harder problems later. Speed here protects the whole paper.
Step 1: Anchor the key equivalents
Everything begins with a small set of facts your child should know instantly, the way they know 7 times 8. Drill these until recall is automatic, then the conversions look after themselves. This is the single highest-value thing you can do for this topic.
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/3 | 0.333... | 33.3% |
| 2/3 | 0.666... | 66.7% |
| 1/5 | 0.2 | 20% |
| 2/5 | 0.4 | 40% |
| 1/10 | 0.1 | 10% |
| 1/8 | 0.125 | 12.5% |
Print this out and stick it on the fridge for a fortnight. Our free worksheets include timed FDP recall drills built around exactly this table.
Step 2: Learn the conversion routes
There are only three journeys to learn, and each has a single reliable method. Teach the method, not a hundred separate examples.
- Fraction to decimal: divide the top by the bottom. So 2/5 means 2 divided by 5, which is 0.4. This is short division, done in your head or on paper.
- Decimal to percentage: multiply by 100 (move the digits two places left). So 0.4 becomes 40%.
- Percentage to fraction: write it over 100 and simplify. So 40% is 40/100, which cancels to 2/5.
Worked example: "What is 0.6 as a fraction?" Write 0.6 as 6/10, then simplify by dividing top and bottom by 2 to get 3/5. Worked example the other way: "What is 2/5 as a percentage?" Do 2 divided by 5 equals 0.4, then times 100 equals 40%. Same two numbers, opposite directions — once a child sees they are reversible, the topic clicks.
Step 3: Percentages of an amount
This is where the marks really live in the exam. The trick is to find 10% first (divide by 10), then build the answer from there. To find 30% of £20, first find 10% (£2), then multiply by 3 to get £6. For 5%, halve your 10%. For 15%, add a 10% and a 5%. This "10% building block" method is faster and less error-prone than any formula.
Worked example with a shopping context: "A £20 jumper has 30% off — what do you pay?" Find 30% of 20 (£6 off), then subtract from the original: 20 minus 6 equals £14. Always identify what the percentage is a percentage of — that is the single most common place children slip.
Common exam traps
These are the specific ways children lose marks on FDP questions in a real 11+ paper. Knowing the traps is half the defence.
- Forgetting to simplify. A correct answer of 4/8 may not be an option — 1/2 is. Always cancel down.
- The "discount versus final price" switch. The last line of a worded problem often asks for what you pay, not the amount saved. Re-read the final sentence.
- Comparing unlike forms. To order 0.7, 3/5 and 65%, convert everything to one form first (here, percentages: 70%, 60%, 65%).
- Mixing up 1/3 as 0.3. One third is 0.333..., not 0.3. This tiny slip changes the answer.
A method for tackling worded FDP problems
When a question is buried in a story, use the same four steps every time so nothing gets missed:
- Underline the actual question in the final sentence.
- List what you are given (the amount, the fraction or percentage).
- Choose the operation — usually find 10% first, or convert to a common form.
- Check units and re-read: does the answer make sense, and did you answer what was asked?
Build this habit on our revision hub and put it under the clock with a timed mock paper. For region-specific practice, the GL papers and CSSE papers pages show how the same skills are dressed differently across boards — CSSE, for instance, is more likely to ask a free-response percentage question than a tidy A-to-E one.
How mastery becomes a score
Getting FDP right quickly does more than earn those specific marks — it frees time for the tougher questions, which lifts the whole raw score. That raw score is then converted into a Standardised (or Standard Age) Score, roughly on a 69 to 141 scale where 100 is average and many grammar schools look for around 111 or above, though exact pass marks vary by area and year. Because the score is age-adjusted, a younger child in the year group is not penalised for their age — but speed on the "easy" topics like this one is what buys the room to shine.
Frequently asked questions
Is a calculator allowed in the 11+?
No. GL maths papers are done without a calculator, which is exactly why the equivalents table above matters so much — fast mental conversion is the whole point.
What year should my child master this?
Aim for confident recall of the key equivalents by the end of Year 5, so that Year 6 can be spent on speed and on harder applications like reverse percentages and ratio.
Which is best to convert to when comparing?
Percentages are usually easiest for ordering and comparing, because everything sits neatly out of 100. Convert all the values to percentages, then line them up.