8 + 5: make ten, then add what remains

Before you start

First practise pairs that make ten, such as 8 and 2. If these are unfamiliar, use counters instead of doing it all mentally.

Work through this example

You have eight counters and receive five more. Find 8 + 5 by completing a group of ten.

Reason step by step

1. Eight needs two more to reach ten: 10 − 8 = 2. Take these two from the group of five.
2. Split five as 2 + 3. The two used to complete ten are no longer part of the remaining group.
3. Now calculate (8 + 2) + 3 = 10 + 3 = 13. Check backwards: 13 − 5 = 8.

A mistake worth understanding

10 + 5 = 15 counts the borrowed two twice. Circle the two counters moved into the ten-group and count only the three left outside.

Try it yourself

Try 9 + 4. Then use the result to solve 13 − 4. Explain how you split four.

Use the idea in the game

Use the add/subtract-to-20 unit on your year map. Making ten is one method; counting on is also valid. Ask the child to explain a method before asking for speed.

About & help

These examples were written for Piko Game. Generated game questions may differ. A score describes a game attempt, not mastery of a school curriculum.

Content and corrections

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