Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 309 · 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. 1.515 − 299 =
2. 2.824 − 798 =
3. 3.765 − 679 =
4. 4.627 − 268 =
5. 5.734 − 199 =
6. 6.174 − 137 =
7. 7.374 − 199 =
8. 8.947 − 167 =
9. 9.441 − 299 =
10. 10.506 − 177 =
11. 11.400 − 298 =
12. 12.592 − 409 =
13. 13.970 − 799 =
14. 14.737 − 369 =
15. 15.548 − 439 =
16. 16.952 − 498 =
17. 17.537 − 498 =
18. 18.830 − 398 =
19. 19.929 − 797 =
20. 20.807 − 117 =
21. 21.942 − 699 =
22. 22.629 − 498 =
23. 23.500 − 459 =
24. 24.826 − 798 =
25. 25.936 − 508 =
26. 26.616 − 447 =
27. 27.738 − 639 =
28. 28.891 − 298 =
29. 29.643 − 548 =
30. 30.530 − 499 =
31. 31.823 − 458 =
32. 32.510 − 209 =
33. 33.243 − 139 =
34. 34.892 − 499 =
35. 35.891 − 187 =
36. 36.778 − 398 =
37. 37.846 − 577 =
38. 38.949 − 397 =
39. 39.713 − 389 =
40. 40.842 − 698 =

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