The idea, step by step
Use a friendly ten
You do not need to count every object one at a time. To find 8 + 5, split 5 into 2 and 3. Add 2 to make 10, then add 3. The total is 13.
Use what you know
Doubles are useful facts: 6 + 6 = 12. Then 6 + 7 is one more, so it is 13. Addition and subtraction undo each other: knowing 7 + 8 = 15 helps with 15 − 7 = 8.
A common trap
Counting the starting number as the first number added.
Instead: For 7 + 3, start at 7 and make three jumps: 8, 9, 10.
See the thinking
Make ten
Find 9 + 6.
- Split 6 into 1 and 5.
- 9 + 1 makes 10; 10 + 5 makes 15.
Use an addition fact
Find 14 − 6.
- Think: 6 plus what makes 14?
- 6 + 8 = 14, so the missing part is 8.
Check your understanding
Find 7 + 6 using a double.
Show answer
13
7 + 7 = 14, so 7 + 6 is one less.
Your turn
6 questions · Work at your own pace.
Read the questions online
- Find 8 + 4.
- Find 6 + 6.
- Find 9 + 8.
- Find 16 − 7.
- Find 13 − 5.
- Explain a way to find 8 + 7 without counting by ones.
Read the worked solutions
- Find 8 + 4.
8 + 2 + 2 = 12.
12 - Find 6 + 6.
Double 6 is 12.
12 - Find 9 + 8.
9 + 1 + 7 = 17.
17 - Find 16 − 7.
7 + 9 = 16.
9 - Find 13 − 5.
5 + 8 = 13.
8 - Explain a way to find 8 + 7 without counting by ones.
Split 7 into 2 and 5, then make ten.
For example, 8 + 2 + 5 = 15.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Facts within 20; one-/two-digit calculations; partitioning; related facts; missing numbers; checking.
Official curriculum source ↗