Helping your child with mental calculation

A group of number dice.

At a glance

  • Most calculations that we carry out each day we do in our heads.
  • Travelling, shopping and getting dinner ready all involve mental calculations.
  • The methods we use when we work things out in our heads are often not the same methods that we use when we write down a sum.
  • Ask your child how they mentally worked out the answer to a question.

Give your kids a boost in maths by encouraging them to work out sums in their head.

Most calculations that we carry out each day we do in our heads. With some calculations we feel the need to reach for paper and pencil or a calculator. Yet when we play a game of darts or cards or even watch a rugby league game, we rely on carrying out lots of mental calculations. How many points are needed to win? How many converted tries will put our team in front and is there enough time?

Travelling, sharing a bill, shopping, playing or watching sport, and getting dinner ready all involve mental calculations. The methods we use when we work things out in our heads are often not the same methods that we use when we write down a sum.

The processes involved in mental calculations have remained a mystery for many kids and even for many adults. Working out 998 x 3 is a hard task, even when using pen and paper if you don't realise that you can find the answer mentally by subtracting 6 from 3,000.

How kids learn to work maths out in their heads?

Kids begin by counting things they can see and using objects to add and subtract. They begin to think of ways to add and subtract without having to use objects. One of the early ways in which kids learn to add two numbers in their head is to start with the larger number and count by ones to add the second number. This is an effective way when adding on small numbers. As children begin to deal with larger numbers they develop a range of ways other than counting by ones.

For example, to find out the answer to 25 + 89, kids could:

  • make the 89 up to 90, then add 10 and then 14
  • add 20 and 80 to make 100, then add 9 and 5 to make 14, then add 100 and 14
  • add 10 twice to 89 and then add 5 more.

One of the interesting things about mental calculations is that people don't all think the same way.

What can parents do to help their kids work out maths in their head?

  • Ask your child how they mentally worked out the answer to a question. Explain how you would mentally work out the answer. If your child can't work out the answer mentally, give them objects to use for counting.
  • Ask your child to work out how much change they will get when paying for something at the shops.
  • If your child is saving to buy something, ask how much more money they will need to save before being able to buy it.
  • Encourage your child to estimate the cost of two items when shopping.
  • When playing games that use two dice, replace dot dice with ones that have numbers on them.
  • If watching a game involving two teams, ask your child to work out mentally the difference in the scores.
  • Involve your child in working out costs associated with holiday travel. For example, "How much will it cost if we stay five nights and the cost each night is $75?"

Helping your child to work out maths in their head in your language


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