An easier way to add numbers in your head

First, let’s make ten

Imagine you have 9 counters. A friend gives you 6 more. How many do you have altogether?

Take one of your friend’s counters and put it beside your nine. You now have 10 counters in one group and 5 left in the other.

Ten and five make 15. You did not add an extra counter or lose one. You just moved one to make the groups easier to count.

That is the idea behind this trick: a number ending in zero is often easier to work with.

Now try it with 38 stickers

You have 38 stickers and get 27 more. We want to find the total: 38 + 27.

1. Pretend you have two extra stickers. Your first pile becomes 40 instead of 38. Remember: those two extras are only pretend.
2. Add the 27 real stickers. First add 20 to 40. That makes 60. Then add the remaining 7. That makes 67.
3. Take away the two pretend stickers. You counted them to make the sum easier, but they were never really there. Two fewer than 67 is 65.

So 38 + 27 is 65. If the last step feels confusing, draw two extra circles in a different colour. Cross them out at the end.

Taking things away works a little differently

Imagine you have 72 stickers and give away 29. How many are left?

1. It is easier to count 30 than 29. Pretend you give away 30: take away 20 first, leaving 52, then another 10, leaving 42.
2. But you only meant to give away 29. You took away one sticker too many.
3. Put that one back. Now you have 43.

Notice the difference. In the first example we added pretend extras, so we took them away. Here we took away too much, so we put one back.

Have a go with one small sum

Try 19 + 6. Make the 19 into 20 by adding one pretend counter. What should you do after adding the six?

You can use real objects, draw dots or write each step. There is no need to do everything in your head straight away.

The one thing to remember

Ask yourself: what did I change? That question matters more than memorising a formula. Once this feels comfortable, try an easy way to multiply by 11.