Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 371 · 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. 1.839 − 797 =
2. 2.940 − 599 =
3. 3.844 − 597 =
4. 4.382 − 308 =
5. 5.902 − 519 =
6. 6.445 − 299 =
7. 7.906 − 228 =
8. 8.485 − 257 =
9. 9.488 − 297 =
10. 10.626 − 298 =
11. 11.843 − 339 =
12. 12.377 − 129 =
13. 13.517 − 498 =
14. 14.477 − 448 =
15. 15.632 − 129 =
16. 16.722 − 509 =
17. 17.751 − 387 =
18. 18.794 − 347 =
19. 19.265 − 207 =
20. 20.670 − 398 =
21. 21.408 − 357 =
22. 22.959 − 498 =
23. 23.882 − 597 =
24. 24.645 − 537 =
25. 25.993 − 199 =
26. 26.706 − 598 =
27. 27.634 − 497 =
28. 28.507 − 399 =
29. 29.522 − 399 =
30. 30.495 − 199 =
31. 31.991 − 698 =
32. 32.623 − 539 =
33. 33.499 − 298 =
34. 34.813 − 299 =
35. 35.994 − 799 =
36. 36.663 − 598 =
37. 37.268 − 238 =
38. 38.961 − 799 =
39. 39.508 − 319 =
40. 40.634 − 568 =

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