Mental maths habits that make kids faster with numbers

Quick sums can feel like a race, but the best first question is often, “What do I already know?” If you know that 8 + 2 = 10, then 8 + 7 can become 8 + 2 + 5. You have changed the shape of the problem without changing its answer. This is a mental maths habit: use a familiar fact to make a new sum easier.

The Education Endowment Foundation's maths guidance says that children need basic number facts and ways to use them, including mental arithmetic. It also recommends a range of calculation methods rather than one trick for every problem (EEF, 2017; EEF, 2018). Here are four habits a family can practise with a pencil, a shopping list or a short game.

Make a ten

Ten is an easy stopping point. To solve 9 + 6, move one from the 6 to the 9. Now you have 10 + 5 = 15. To solve 38 + 7, move two from the 7 to the 38. Now you have 40 + 5 = 45. Ask a child to show the moved part with counters if the idea feels slippery.

This is not a rule to memorise without understanding. Ask why 9 + 6 and 10 + 5 must have the same answer. The total stays the same because one part gets one larger while the other gets one smaller. Once that makes sense, the child can choose this method when a number sits near a ten.

Try a few: 8 + 5, 29 + 4 and 47 + 6. Let the child explain the step out loud. If a different correct method is easier for them, keep it. The aim is a useful choice, not a compulsory script.

Split a number into parts

For 36 + 22, add tens and ones separately: 30 + 20 = 50, and 6 + 2 = 8, so the total is 58. For 47 + 18, you might add 10 first to reach 57, then add 8 to reach 65. Both routes preserve the same total.

Breaking a problem into parts also helps with subtraction. To work out 63 - 18, take away 10 to reach 53, then 8 to reach 45. You can check by adding 18 back to 45. This habit is useful because you can see where an error entered. Did you lose a ten or a one? A calculator can confirm the answer, but explaining the route shows what the child understood.

The Institute of Education Sciences recommends clear instruction, number lines and representations for children who struggle with elementary maths. A number line can show the two jumps in 63 - 18 far better than an instruction to “just do it in your head” (IES, 2021).

Estimate before you answer

Suppose the question is 48 + 31. Before calculating exactly, notice that 48 is near 50 and 31 is near 30, so the answer should be near 80. The exact total, 79, fits. An answer of 179 cannot be right. Estimation is a simple check, not a replacement for the exact answer.

For a child starting out, use smaller numbers: 19 + 21 is near 20 + 20. Ask whether an answer is reasonable before asking how fast it came. This helps separate two jobs: finding a result and checking it. In a timed game, a quick sense check can prevent a rushed tap.

Learn from the wrong answer

If a child says 8 + 7 = 14, ask how they got there. Maybe they counted one step too few. Maybe they used a known double, 7 + 7, and forgot the extra one. The mistake gives a clue about what to practise next. The EEF guidance asks teachers to address common misconceptions, and the IES guide stresses systematic instruction and representations (EEF, 2017; IES, 2021). A calm explanation is more helpful than saying “faster.”

Speed can come after a method feels familiar. At first, let the child work without a clock. Later, a short timed round can make recall fun. If the timer makes them guess, return to untimed examples. One fast score is not a better measure of understanding than a clearly explained answer.

Try a short round

Quick Sums asks players to pick an answer before time runs out. After a round, choose one sum and ask, “Could you solve it another way?” Look for a ten, split it into parts, or estimate before choosing. Practice can improve your scores in this game. The bigger lesson is knowing which method makes a particular sum clear to you, even when there is no timer at all.