The idea, step by step
Split to help yourself
Partition means split into parts. 27 can be 20 + 7, but it can also be 3 + 24. Choose the split that helps your calculation. For 47 + 6, split the 6 into 3 + 3 so you can make 50.
Keep all the parts
If you split 18 into 10 + 8, both parts must be used. For 63 − 18, subtract 10 to get 53, then subtract 8 to get 45. A jump drawing lets you check that the jumps total 18.
A common trap
Splitting 7 into 2 and 5 but using only the 2.
Instead: Both parts belong to the original 7. Record each jump and check their total.
See the thinking
Cross a ten when adding
Find 56 + 8.
- Split 8 into 4 and 4.
- 56 + 4 = 60; 60 + 4 = 64.
Cross a ten when subtracting
Find 42 − 7.
- Split 7 into 2 and 5.
- 42 − 2 = 40; 40 − 5 = 35.
Check your understanding
Use 10 + 6 to find 35 + 16.
Show answer
51
35 + 10 = 45; 45 + 6 = 51.
Your turn
6 questions · Work at your own pace.
Read the questions online
- Split 38 into tens and ones.
- Find 28 + 7 by making 30 first.
- Find 71 − 6 by reaching 70 first.
- Find 44 + 23 using 20 + 3.
- Find 85 − 17 using 10 + 7.
- Mina splits 9 into 4 + 5 to find 36 + 9. Finish her method.
Read the worked solutions
- Split 38 into tens and ones.
3 tens are 30 and there are 8 ones.
30 + 8 - Find 28 + 7 by making 30 first.
Split 7 as 2 + 5: 28 + 2 + 5 = 35.
35 - Find 71 − 6 by reaching 70 first.
Split 6 as 1 + 5: 71 − 1 − 5 = 65.
65 - Find 44 + 23 using 20 + 3.
44 + 20 = 64; 64 + 3 = 67.
67 - Find 85 − 17 using 10 + 7.
85 − 10 = 75; 75 − 7 = 68.
68 - Mina splits 9 into 4 + 5 to find 36 + 9. Finish her method.
36 + 4 = 40; 40 + 5 = 45.
45
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 ↗