Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 648 · 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. 1.650 − 429 =
2. 2.539 − 299 =
3. 3.713 − 378 =
4. 4.501 − 298 =
5. 5.853 − 497 =
6. 6.680 − 497 =
7. 7.994 − 398 =
8. 8.777 − 178 =
9. 9.925 − 678 =
10. 10.912 − 289 =
11. 11.510 − 267 =
12. 12.602 − 498 =
13. 13.504 − 369 =
14. 14.343 − 218 =
15. 15.897 − 658 =
16. 16.991 − 697 =
17. 17.834 − 798 =
18. 18.973 − 269 =
19. 19.937 − 597 =
20. 20.808 − 597 =
21. 21.731 − 697 =
22. 22.667 − 598 =
23. 23.700 − 598 =
24. 24.566 − 408 =
25. 25.657 − 399 =
26. 26.733 − 697 =
27. 27.919 − 499 =
28. 28.500 − 399 =
29. 29.436 − 299 =
30. 30.918 − 299 =
31. 31.418 − 299 =
32. 32.246 − 208 =
33. 33.733 − 309 =
34. 34.846 − 299 =
35. 35.940 − 219 =
36. 36.637 − 539 =
37. 37.718 − 298 =
38. 38.990 − 699 =
39. 39.956 − 397 =
40. 40.279 − 138 =

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