Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 700 · 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. 1.768 − 399 =
2. 2.802 − 278 =
3. 3.979 − 629 =
4. 4.763 − 397 =
5. 5.838 − 619 =
6. 6.665 − 609 =
7. 7.591 − 498 =
8. 8.565 − 119 =
9. 9.847 − 398 =
10. 10.969 − 579 =
11. 11.735 − 627 =
12. 12.530 − 147 =
13. 13.508 − 397 =
14. 14.520 − 498 =
15. 15.534 − 197 =
16. 16.984 − 799 =
17. 17.475 − 299 =
18. 18.748 − 238 =
19. 19.721 − 639 =
20. 20.636 − 367 =
21. 21.714 − 429 =
22. 22.882 − 399 =
23. 23.331 − 299 =
24. 24.514 − 299 =
25. 25.790 − 498 =
26. 26.396 − 367 =
27. 27.879 − 599 =
28. 28.258 − 188 =
29. 29.847 − 698 =
30. 30.413 − 317 =
31. 31.962 − 198 =
32. 32.908 − 599 =
33. 33.398 − 247 =
34. 34.900 − 697 =
35. 35.599 − 498 =
36. 36.787 − 597 =
37. 37.305 − 199 =
38. 38.936 − 288 =
39. 39.241 − 199 =
40. 40.290 − 198 =

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