Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 815 · 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. 1.705 − 189 =
2. 2.762 − 687 =
3. 3.871 − 579 =
4. 4.600 − 577 =
5. 5.433 − 287 =
6. 6.564 − 417 =
7. 7.810 − 698 =
8. 8.909 − 199 =
9. 9.982 − 598 =
10. 10.959 − 299 =
11. 11.695 − 199 =
12. 12.546 − 498 =
13. 13.665 − 299 =
14. 14.836 − 299 =
15. 15.787 − 698 =
16. 16.850 − 398 =
17. 17.642 − 287 =
18. 18.938 − 699 =
19. 19.901 − 799 =
20. 20.599 − 148 =
21. 21.779 − 699 =
22. 22.581 − 299 =
23. 23.945 − 798 =
24. 24.899 − 197 =
25. 25.906 − 637 =
26. 26.636 − 617 =
27. 27.897 − 157 =
28. 28.599 − 299 =
29. 29.972 − 397 =
30. 30.610 − 199 =
31. 31.967 − 598 =
32. 32.529 − 297 =
33. 33.688 − 599 =
34. 34.869 − 648 =
35. 35.469 − 388 =
36. 36.607 − 447 =
37. 37.908 − 498 =
38. 38.252 − 199 =
39. 39.167 − 117 =
40. 40.614 − 597 =

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