Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 508 · 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. 1.644 − 589 =
2. 2.679 − 198 =
3. 3.839 − 497 =
4. 4.671 − 597 =
5. 5.689 − 299 =
6. 6.578 − 479 =
7. 7.798 − 308 =
8. 8.858 − 798 =
9. 9.790 − 699 =
10. 10.683 − 287 =
11. 11.823 − 499 =
12. 12.797 − 639 =
13. 13.844 − 799 =
14. 14.615 − 299 =
15. 15.812 − 799 =
16. 16.868 − 199 =
17. 17.515 − 207 =
18. 18.782 − 297 =
19. 19.997 − 798 =
20. 20.614 − 598 =
21. 21.585 − 367 =
22. 22.532 − 398 =
23. 23.526 − 197 =
24. 24.987 − 189 =
25. 25.900 − 398 =
26. 26.850 − 227 =
27. 27.714 − 397 =
28. 28.917 − 499 =
29. 29.887 − 197 =
30. 30.450 − 187 =
31. 31.682 − 379 =
32. 32.814 − 277 =
33. 33.897 − 397 =
34. 34.924 − 797 =
35. 35.702 − 677 =
36. 36.734 − 519 =
37. 37.742 − 328 =
38. 38.999 − 659 =
39. 39.654 − 168 =
40. 40.826 − 198 =

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