The 11+ rewards speed almost as much as accuracy. In a typical GL Assessment maths paper you face around 50 questions in 50 minutes, roughly one minute each, multiple-choice with answers A to E on a separate OMR sheet, and no calculator. A child who can shave five seconds off each calculation buys back several minutes to check work and rescue the hard questions at the end. Mental maths shortcuts are how strong candidates create that time. Below are the core techniques, each shown step by step, with the exam traps that quietly cost marks.
Why mental shortcuts matter in the modern 11+
Since CEM's separate 11+ tests were phased out around 2022-2023, GL Assessment now dominates most regions, alongside bespoke and consortium papers such as the CSSE exam in Essex. Whatever the board, the pressure is the same: tight timing and no calculator. Your raw score is converted into a Standard Age Score (SAS, roughly 69-141, with 100 as average and often around 111+ needed for a grammar place), and age-standardisation helps younger pupils slightly. But the surest route to a high SAS is finishing the paper calmly with time to check. Fluency, not frantic scribbling, is what these shortcuts build. Practise them on our free worksheets and time yourself against an on-site mock paper.
1. Round and adjust
To add a number close to a round figure, jump to the round figure and adjust. To add 199, add 200 and subtract 1. To multiply by 19, multiply by 20 and subtract one lot of the number: 34 × 19 = (34 × 20) − 34 = 680 − 34 = 646. This partitioning trick works because it swaps an awkward calculation for an easy one plus a tiny correction.
Exam trap: children forget the direction of the adjustment. Adding 199 means subtracting 1 after adding 200; multiplying by 21 means adding one lot, not subtracting. Whisper "up then back down, or down then up" as a check.
2. Multiply by 5 by using tens and halving
Any number times 5 is the same number times 10, then halved. 34 × 5 = (34 × 10) ÷ 2 = 340 ÷ 2 = 170. It is far quicker than laying out long multiplication and much less error-prone. The same idea multiplies by 50 (times 100, then halve) and by 25 (times 100, then divide by 4).
3. Use complements for subtraction
Subtracting from a round number is faster if you count up rather than borrow across zeros. For 1000 − 367, count on from 367: 367 to 400 is 33, and 400 to 1000 is 600, so the answer is 633. This "shopkeeper's method" removes the messy column borrowing where most slips happen. Try it on the worded questions in our revision hub.
4. Halve and double
When one factor is even and the other is awkward, halve the even one and double the other. 16 × 25 = 8 × 50 = 4 × 100 = 400. Keep halving and doubling until one factor becomes a friendly 10, 50 or 100. This is a favourite for questions involving 25, 50 and 250.
5. Spot the easy fraction, decimal and percentage
Recognising common equivalents saves working from scratch. 75% is three quarters; 60% is three fifths; 20% is one fifth. To find 15% of an amount, find 10% (divide by 10) then add half of that again. The table below is worth memorising cold, and it links directly to our fuller guide on fractions, decimals and percentages.
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 3/5 | 0.6 | 60% |
| 1/10 | 0.1 | 10% |
| 1/3 | 0.33... | 33.3% |
More shortcuts worth banking
- Times 9: multiply by 10 and subtract one lot. 7 × 9 = 70 − 7 = 63.
- Times 11 (two-digit): for 11 × 36, add the digits (3 + 6 = 9) and drop it in the middle: 396.
- Divide by 5: double the number, then divide by 10. 245 ÷ 5 = 490 ÷ 10 = 49.
- Percentage building blocks: find 10% and 1%, then combine. 23% of 400 = (10%×2) + (1%×3) = 80 + 12 = 92.
- Adjust for averages: to find the mean of numbers close together, pick a base and average the differences.
A method for multi-step worded problems
Shortcuts only help if you attack the right calculation. On worded questions, use a fixed routine so speed never turns into carelessness:
- Underline exactly what the last sentence asks for.
- List the numbers given and their units.
- Choose the operation, then apply a mental shortcut.
- Check the answer is sensible and matches the answer options A-E.
Exam trap: the final sentence often switches the question ("how much change?" not "how much did it cost?"). Estimate first, then pick the closest option, so a slip in mental arithmetic still lands near the right answer. For fuller worked routines, see our post on tackling 11+ word problems and the exam guides.
Building fluency by year group
These shortcuts are Year 4 and 5 friendly for number bonds, times tables and halving/doubling, with the percentage and average tricks best consolidated in Year 6. Regular, short bursts beat long cramming: ten timed questions a day builds the automatic recall the 11+ demands. Track your progress on the live leaderboard and see the full timetable on our key dates page.
Frequently asked questions
Is a calculator allowed in the 11+?
No. GL, CSSE and independent-school pre-tests are all non-calculator, which is exactly why mental shortcuts are so valuable.
How much time do I get per question?
In a standard GL paper of around 50 questions in 50 minutes, roughly one minute each. Shortcuts free up time to check and to finish the harder final questions.
Which shortcut should my child learn first?
Start with round-and-adjust and the times-tables tricks (5, 9, 10, 11), then the fraction-decimal-percentage equivalents. These appear most often and unlock the widest range of questions.