Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 634 · 40 questions

How to do it in your head (Round up, add back): Round the number you take away up to the next ten or hundred: 297 → 300 (3 too many). Take away the round number. Add back the extra, because you took away too much.

1. 1.486 − 299 =
2. 2.258 − 197 =
3. 3.677 − 199 =
4. 4.778 − 597 =
5. 5.907 − 629 =
6. 6.909 − 198 =
7. 7.887 − 497 =
8. 8.876 − 628 =
9. 9.979 − 799 =
10. 10.776 − 698 =
11. 11.972 − 798 =
12. 12.872 − 398 =
13. 13.626 − 179 =
14. 14.639 − 597 =
15. 15.465 − 398 =
16. 16.704 − 199 =
17. 17.525 − 499 =
18. 18.523 − 498 =
19. 19.323 − 309 =
20. 20.580 − 147 =
21. 21.789 − 198 =
22. 22.933 − 797 =
23. 23.488 − 399 =
24. 24.999 − 499 =
25. 25.712 − 198 =
26. 26.920 − 577 =
27. 27.855 − 147 =
28. 28.724 − 699 =
29. 29.533 − 497 =
30. 30.783 − 398 =
31. 31.368 − 157 =
32. 32.805 − 258 =
33. 33.932 − 398 =
34. 34.712 − 328 =
35. 35.725 − 659 =
36. 36.519 − 399 =
37. 37.574 − 477 =
38. 38.689 − 599 =
39. 39.936 − 497 =
40. 40.903 − 397 =

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