Counting back to ten
You learn how much to take away from a number between 10 and 20 to get to exactly ten.
How to work it out
- Split the teen number into ten and ones: 16 is 10 and 6.
- Subtract the ones to land exactly on ten.
16 − _ = 10
- Partition 16 into 10 and 6.
- Take away the 6 ones.
- So 16 − 6 = 10.
More examples
13 − _ = 10
- Partition 13 into 10 and 3.
- Take away the 3 ones.
- So 13 − 3 = 10.
19 − _ = 10
- Partition 19 into 10 and 9.
- Take away the 9 ones.
- So 19 − 9 = 10.