Mental Maths Tricks: Children who spot patterns in numbers are not just good at maths, they think like mathematicians. The UK National Curriculum for Key Stage 2 asks pupils not only to calculate accurately but to reason mathematically, which means understanding why a method works, not just following a procedure. Mental maths tricks give children exactly that: a window into the structure of numbers that makes arithmetic faster, less stressful, and genuinely interesting.
LearningMole has spent years watching primary children light up when a number trick produces a result they cannot immediately explain. That moment of surprise is not a distraction from learning; it is the learning. When a child asks, “But how does that always work?”, they are doing the most valuable thing a young mathematician can do. The tricks in this guide are rooted in the same properties of numbers that underpin KS2 arithmetic, and each one includes an explanation designed to satisfy that curiosity.
This guide is written for UK primary teachers looking for engaging ways to build number fluency, and for parents who want to make maths feel less like homework and more like play. The eight tricks below cover multiplication, subtraction, and addition strategies that are genuinely useful in SATs arithmetic papers and the Year 4 Multiplication Tables Check. By the end, children will not just know the tricks — they will understand why they work.
Mental arithmetic is one of the strongest predictors of later maths confidence. Children who can manipulate numbers in their heads are not just faster at sums; they are more flexible thinkers who make fewer errors when checking written calculations. The UK National Curriculum explicitly requires KS2 pupils to recall and use multiplication and division facts, perform mental calculations with mixed operations, and estimate to check answers. Mental maths tricks build all three skills simultaneously.
Speed matters in formal assessments, too. The Year 6 SATs Arithmetic Paper is timed, and pupils who rely on written methods for every question run out of time. A child who can multiply by 11 mentally, or subtract from 1,000 in seconds, gains back precious time for the harder questions. The Year 4 Multiplication Tables Check (MTC) specifically tests speed and accuracy on times tables up to 12 × 12 under time pressure. The strategies in this guide translate directly into those assessment contexts.
Beyond tests, mental agility builds what teachers sometimes call “number sense”, an intuitive feel for whether an answer is roughly right, whether a calculation can be simplified, and which numbers are hiding useful relationships. That sense does not develop from worksheets alone. It develops through play, patterns, and the kind of structured curiosity that a good maths trick produces.
| Trick | Best For | Key Stage | Difficulty (1–5) |
|---|---|---|---|
| The Magic of 11 | Multiplication | KS2 | 2 |
| All From 9, Last From 10 | Subtraction from 1,000 | KS2 | 3 |
| The 9s Finger Trick | Times tables | KS1–KS2 | 1 |
| Half and Ten (×5) | Multiplication | KS1–KS2 | 1 |
| Squaring Numbers Ending in 5 | Multiplication | KS2 | 3 |
| Double and Halve | Large multiplication | KS2 | 3 |
| Adding Near Doubles | Addition | KS1–KS2 | 2 |
| The Calendar Trick | Day calculation | KS2 | 4 |
Multiplying by 11 is one of the most satisfying tricks in mental arithmetic, and it works every time.
The trick: To multiply any two-digit number by 11, split the digits apart and add them together, then place the sum between the two original digits.
Example: 23 × 11
Example: 45 × 11
What if the middle sum is 10 or more? Example: 76 × 11
How it works: When you multiply any number by 11, you are effectively multiplying by (10 + 1). So 23 × 11 = 23 × 10 + 23 × 1 = 230 + 23 = 253. The trick is a shortcut to the distributive property, and pointing it out to KS2 children gives them genuine algebraic insight.
Classroom use: Use this as a starter activity. Call out a two-digit number, and challenge children to give the answer before you can write it down. They will win every time within a week of practice.
Subtraction from round numbers is a common stumbling block. This rule makes it almost instant.
The trick: To subtract any three-digit number from 1,000, subtract each digit from 9, except the last digit, which you subtract from 10.
Example: 1,000 − 374
Example: 1,000 − 851
How it works: This is a direct consequence of borrowing in column subtraction. When you borrow through a chain of zeros, each digit ends up being taken from 9, except the last, which is taken from 10. Understanding this demystifies borrowing and reduces the errors children make in written subtraction.
Curriculum link: Subtraction strategies, including counting up (complementary addition), appear in the KS2 National Curriculum from Year 3 onwards. This trick sits naturally alongside those methods as an alternative mental strategy.
This trick is beloved by Year 3 and Year 4 teachers because it is entirely physical and requires no paper.
The trick: Hold both hands in front of you, palms facing away. Number your fingers 1–10 from left to right. To multiply any number from 1 to 10 by 9, fold down the finger that matches the number you are multiplying by.
Example: 9 × 4
Example: 9 × 7
How it works: The 9 times table has a pattern — the tens digit increases by 1 and the units digit decreases by 1 for each step (9, 18, 27, 36…). The finger trick represents this pattern spatially, which is particularly effective for visual and kinaesthetic learners.
For parents: This is one of the most useful tricks to teach at home before the Year 4 MTC. Children who use their fingers as a backup check feel much more confident when the timer starts.
This trick works for any number, not just the ones in the five times table.
The trick: To multiply any number by 5, halve the number, then multiply by 10.
Example: 5 × 46
Example: 5 × 37
How it works: Multiplying by 5 is the same as multiplying by 10 then dividing by 2 (10/2 = 5). For odd numbers, the half produces a decimal (like 18.5) which resolves cleanly when multiplied by 10.
Classroom extension: Once children understand this trick, introduce the reverse: dividing by 5 means doubling and dividing by 10. This builds the multiplicative reasoning KS2 children need for fractions and ratios.
This trick feels like real magic until children see the pattern underneath it.
The trick: To square any number ending in 5, multiply the first digit(s) by the next number up, then write 25 at the end.
Example: 35²
Example: 75²
How it works: Any number ending in 5 can be written as (10n + 5). Squaring it gives 100n² + 100n + 25 = 100n(n+1) + 25. That last term is always 25, and 100n(n+1) always ends in two zeros — so the first part is simply n(n+1) followed by 25.
This technique simplifies multiplication that looks difficult by turning it into an easier one.
The trick: Double one number and halve the other. The product stays the same.
Example: 16 × 25
Example: 14 × 35
Example: 24 × 125
How it works: (2a) × (b/2) = ab. This is the same principle used in the ancient Egyptian multiplication method, which makes for an interesting historical diversion with older KS2 children.
Curriculum link: This strategy directly supports the KS2 objective to use known facts and place value to multiply mentally. It also builds fluency with factors and multiples.
Children who know their doubles facts can use this trick to add numbers that are close to each other much faster.
The trick: If two numbers are close to each other, double the smaller one and add the difference.
Example: 7 + 8
Example: 48 + 51
How it works: This is a form of the “compensating” strategy — adjusting from a known fact (the double) to the actual sum. For EYFS and KS1 children, start with numbers up to 10; KS2 children can apply it to two- and three-digit numbers.
This trick produces the biggest reactions with older KS2 children and pulls together several mental arithmetic skills at once.
The trick: Tell someone their birthday month and date. You calculate the day of the week it falls on in the current year.
How to do it for 2025 (adjust the year offset for other years):
| Month | Code | Month | Code |
|---|---|---|---|
| January | 1 | July | 0 |
| February | 4 | August | 3 |
| March | 4 | September | 6 |
| April | 0 | October | 1 |
| May | 2 | November | 4 |
| June | 5 | December | 6 |
Example: 15th April 2025
How it works: The trick uses modular arithmetic, the same mathematics behind computer clocks and cryptography. Older KS2 children love discovering that “clock arithmetic” has real-world applications far beyond the classroom.
The Year 6 SATs Arithmetic Paper awards one mark per question and runs to 36 questions in 30 minutes. That gives roughly 50 seconds per question. For pupils using written column methods for every single calculation, the clock becomes the enemy.
Mental strategies save time on specific question types that appear consistently in the Arithmetic Paper. Multiplications involving 11 or 5 as a factor can be answered mentally in under five seconds. Subtractions from round numbers become one-step calculations rather than multi-column borrows. Near-doubles additions take two steps rather than four. The cumulative time saved across a 36-question paper can be four to six minutes, transformative for pupils who find the test tight.
“Children who understand number relationships rather than just following written procedures are far more resilient in timed tests. The goal isn’t to teach tricks as shortcuts; it’s to build the flexible thinking that lets children choose the most efficient approach for each question.” — Michelle Connolly, Founder of LearningMole and former teacher with over 15 years of classroom experience
The same logic applies to the Year 4 Multiplication Tables Check. The MTC tests each fact with a six-second window per question. Pupils who use the 9s finger trick as a backup for uncertain facts make fewer errors under time pressure. The tricks are not a replacement for fluent recall; they are a safety net that prevents panic when recall temporarily fails.
For teachers: the most effective SATs preparation includes one “trick of the week” from October onwards, revisited in morning registration for three to five minutes. By February, children have a toolkit of six to eight strategies they can deploy automatically.
LearningMole’s primary maths resources include curriculum-aligned videos and activities covering multiplication, addition, subtraction, and mental calculation strategies for KS1 and KS2. The video resources are designed to make abstract number relationships visible, exactly the kind of visual support that helps the tricks in this guide move from “magic” to understood technique.
For teachers preparing classes for the Year 4 MTC or the Year 6 SATs Arithmetic Paper, LearningMole’s maths videos work well as starter content before introducing written practice. Browse LearningMole’s primary maths resources to find curriculum-aligned videos covering multiplication tables, mental calculation strategies, and number fluency for every year group from Reception to Year 6.
For parents supporting home learning, the videos provide clear, jargon-free explanations that give children the same foundations their teacher is building in the classroom. Pairing a LearningMole video with five minutes of trick practice at the kitchen table is one of the most effective ways to build number confidence outside school.
The most effective approach is “little and often.” Five minutes of daily practice on a single specific trick yields more durable results than an hour of mixed worksheets once a week. Start with the trick your child finds most engaging, often the 9s finger trick or the 11s method and practise it until it feels automatic before introducing another. LearningMole’s maths videos work well as a warm-up before home practice sessions. Connecting tricks to real situations (e.g., multiplying by 5 when working out prices) helps consolidate understanding of the method.
The 9s finger trick is the best starting point for most children in Years 3 and 4 because it requires no paper and produces instant results. The “Half and Ten” strategy for multiplying by 5 is almost as simple and applies to a wider range of numbers. In addition, adding near doubles is the most accessible entry point. The 11s trick tends to be most popular with older KS2 children because the step-by-step method is satisfying and the results look impressive.
Yes. Mental strategies are valid arithmetic methods that lead to the correct answer. The SATs Arithmetic Paper does not specify how pupils must reach an answer; it marks the correct result. Tricks rooted in number properties reinforce rather than replace conceptual knowledge, and using mental strategies for appropriate questions is exactly the flexible approach the National Curriculum describes.
Basic mental strategies can start from Year 1, particularly number bonds to 10 and doubling small numbers. The “Half and Ten” strategy for multiplying by 5 is accessible from Year 2 or 3. The 9s finger trick works well from Year 3. The more complex tricks, squaring numbers ending in 5, the Double and Halve technique, and the Calendar Trick, are best introduced in Years 5 and 6.
The Bridge to 10 (sometimes called “making ten”) is a method for adding two numbers by first reaching the nearest ten, then adding the remainder. For example, to calculate 8 + 6: split 6 into 2 and 4, add the 2 to 8 to make 10, then add the remaining 4 to get 14. This is one of the most important early mental strategies in the KS1 curriculum and underpins efficient addition for much larger numbers.
LearningMole provides curriculum-aligned maths resources covering mental calculation strategies, times tables practice, and arithmetic fluency for every primary year group. Visit LearningMole’s maths section for videos and activities covering the strategies described in this guide, organised by key stage and learning objective.
A child with solid mental maths skills can explain their method, not just produce an answer. Ask them to talk through how they reached a result: if they can say “I halved 46 to get 23 and then multiplied by 10 to get 230”, they understand the strategy. A useful check is to give them an unfamiliar calculation and watch whether they adapt a known strategy or reach for a pencil immediately. Flexible adaptation is the target.
The UK National Curriculum for mathematics at KS2 requires pupils to recall multiplication and division facts, use place value and known facts to solve problems, perform mental calculations with mixed operations, and reason mathematically by identifying and explaining number patterns. The tricks in this guide address all four requirements: the 11s trick and Double and Halve develop flexible multiplication, the “All From 9” rule develops subtraction fluency, near doubles develops addition reasoning, and the Calendar Trick builds modular reasoning and pattern recognition.
These eight tricks are not shortcuts around understanding; they are routes into it. A child who can multiply any two-digit number by 11 mentally, and who knows why the method works, has a genuine insight into the distributive property of multiplication. A child who can subtract from 1,000 in under five seconds understands what borrowing actually does. The magic is the motivation; the mathematics is the reward.
Bring these tricks into morning registration, homework sessions, or car journeys, and you will quickly see the difference between children who know maths and children who think mathematically. The goal of primary mathematics education in the UK is not just accurate calculation, but confident, flexible reasoning. Mental maths tricks are one of the fastest ways to build both at once.
LearningMole’s curriculum-aligned maths videos and resources support every stage of this journey, from early number bonds in Reception to SATs arithmetic strategies in Year 6. Explore LearningMole’s maths resources to find teacher-designed content that pairs well with the strategies in this guide.
Leave a Reply