Making up to a round number
You learn how much to add or take away to reach a round ten, hundred or thousand.
How to work it out
- Look at the last digit of the number.
- Going up: make the ones up to ten.
- Going down: take the ones away.
- Going to 100 or 1000? First jump to the next ten or hundred.
62 + _ = 100
- Jump to the next ten: 62 + 8 = 70.
- Jump to 100: 70 + 30 = 100.
- Add the jumps: 8 + 30 = 38.
More examples
76 + _ = 80
- Look at the ones: 6.
- Make them up to ten: 6 + 4 = 10.
- So 76 + 4 = 80.
56 − _ = 50
- Look at the ones: 6.
- Take them away.
- So 56 − 6 = 50.
375 + _ = 1000
- Jump to the next hundred: 375 + 25 = 400.
- Jump to 1000: 400 + 600 = 1000.
- Add the jumps: 25 + 600 = 625.