Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 667 · 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. 1.729 − 298 =
2. 2.362 − 297 =
3. 3.793 − 429 =
4. 4.508 − 397 =
5. 5.761 − 199 =
6. 6.222 − 138 =
7. 7.464 − 159 =
8. 8.494 − 398 =
9. 9.978 − 798 =
10. 10.878 − 668 =
11. 11.879 − 697 =
12. 12.983 − 798 =
13. 13.897 − 799 =
14. 14.656 − 168 =
15. 15.866 − 598 =
16. 16.670 − 399 =
17. 17.508 − 438 =
18. 18.915 − 589 =
19. 19.684 − 657 =
20. 20.581 − 399 =
21. 21.753 − 637 =
22. 22.808 − 358 =
23. 23.821 − 799 =
24. 24.886 − 599 =
25. 25.419 − 197 =
26. 26.476 − 207 =
27. 27.641 − 299 =
28. 28.606 − 528 =
29. 29.779 − 237 =
30. 30.227 − 158 =
31. 31.891 − 589 =
32. 32.999 − 609 =
33. 33.564 − 397 =
34. 34.959 − 798 =
35. 35.720 − 497 =
36. 36.744 − 599 =
37. 37.718 − 698 =
38. 38.669 − 598 =
39. 39.935 − 579 =
40. 40.970 − 797 =

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