Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 20 · 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. 1.808 − 629 =
2. 2.397 − 167 =
3. 3.990 − 798 =
4. 4.778 − 598 =
5. 5.903 − 697 =
6. 6.683 − 598 =
7. 7.499 − 399 =
8. 8.709 − 438 =
9. 9.608 − 197 =
10. 10.538 − 397 =
11. 11.815 − 198 =
12. 12.361 − 158 =
13. 13.781 − 687 =
14. 14.484 − 279 =
15. 15.793 − 699 =
16. 16.890 − 498 =
17. 17.628 − 469 =
18. 18.670 − 579 =
19. 19.701 − 598 =
20. 20.786 − 697 =
21. 21.820 − 598 =
22. 22.367 − 297 =
23. 23.900 − 799 =
24. 24.888 − 258 =
25. 25.448 − 298 =
26. 26.843 − 497 =
27. 27.414 − 289 =
28. 28.449 − 399 =
29. 29.534 − 159 =
30. 30.903 − 298 =
31. 31.561 − 397 =
32. 32.580 − 328 =
33. 33.573 − 399 =
34. 34.565 − 497 =
35. 35.861 − 797 =
36. 36.315 − 197 =
37. 37.843 − 309 =
38. 38.905 − 299 =
39. 39.969 − 599 =
40. 40.899 − 307 =

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