Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 820 · 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. 1.647 − 499 =
2. 2.432 − 198 =
3. 3.907 − 798 =
4. 4.488 − 267 =
5. 5.638 − 397 =
6. 6.964 − 549 =
7. 7.547 − 399 =
8. 8.609 − 479 =
9. 9.775 − 458 =
10. 10.808 − 597 =
11. 11.855 − 799 =
12. 12.513 − 197 =
13. 13.981 − 397 =
14. 14.235 − 198 =
15. 15.752 − 589 =
16. 16.525 − 398 =
17. 17.439 − 399 =
18. 18.800 − 287 =
19. 19.786 − 649 =
20. 20.840 − 197 =
21. 21.640 − 358 =
22. 22.304 − 198 =
23. 23.667 − 629 =
24. 24.765 − 659 =
25. 25.487 − 198 =
26. 26.470 − 379 =
27. 27.871 − 799 =
28. 28.568 − 188 =
29. 29.382 − 299 =
30. 30.908 − 198 =
31. 31.908 − 798 =
32. 32.394 − 299 =
33. 33.721 − 698 =
34. 34.931 − 628 =
35. 35.569 − 488 =
36. 36.993 − 578 =
37. 37.988 − 349 =
38. 38.692 − 297 =
39. 39.722 − 398 =
40. 40.830 − 598 =

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