Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 485 · 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. 1.637 − 439 =
2. 2.733 − 597 =
3. 3.945 − 397 =
4. 4.816 − 298 =
5. 5.418 − 198 =
6. 6.369 − 309 =
7. 7.390 − 307 =
8. 8.957 − 697 =
9. 9.747 − 148 =
10. 10.682 − 238 =
11. 11.954 − 219 =
12. 12.864 − 398 =
13. 13.621 − 457 =
14. 14.737 − 699 =
15. 15.476 − 199 =
16. 16.841 − 477 =
17. 17.828 − 648 =
18. 18.547 − 179 =
19. 19.843 − 799 =
20. 20.691 − 599 =
21. 21.744 − 328 =
22. 22.751 − 697 =
23. 23.812 − 569 =
24. 24.251 − 198 =
25. 25.803 − 499 =
26. 26.817 − 599 =
27. 27.560 − 499 =
28. 28.802 − 679 =
29. 29.723 − 648 =
30. 30.342 − 197 =
31. 31.217 − 199 =
32. 32.495 − 429 =
33. 33.787 − 699 =
34. 34.679 − 297 =
35. 35.913 − 498 =
36. 36.649 − 278 =
37. 37.635 − 197 =
38. 38.738 − 199 =
39. 39.416 − 317 =
40. 40.838 − 797 =

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