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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 668 · 40 questions
TalentJR

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.

NameDateTime takenScore ___ / 40
  1. 1.983 − 799 =
  2. 2.785 − 347 =
  3. 3.794 − 498 =
  4. 4.537 − 299 =
  5. 5.967 − 597 =
  6. 6.677 − 597 =
  7. 7.807 − 697 =
  8. 8.771 − 199 =
  9. 9.466 − 298 =
  10. 10.970 − 398 =
  11. 11.693 − 568 =
  12. 12.908 − 198 =
  13. 13.837 − 197 =
  14. 14.425 − 338 =
  15. 15.971 − 498 =
  16. 16.780 − 699 =
  17. 17.946 − 798 =
  18. 18.765 − 239 =
  19. 19.671 − 599 =
  20. 20.904 − 658 =
  21. 21.809 − 159 =
  22. 22.355 − 278 =
  23. 23.530 − 449 =
  24. 24.925 − 377 =
  25. 25.683 − 528 =
  26. 26.640 − 589 =
  27. 27.311 − 218 =
  28. 28.298 − 197 =
  29. 29.944 − 599 =
  30. 30.740 − 198 =
  31. 31.574 − 499 =
  32. 32.544 − 397 =
  33. 33.675 − 657 =
  34. 34.727 − 217 =
  35. 35.545 − 399 =
  36. 36.866 − 658 =
  37. 37.470 − 299 =
  38. 38.357 − 209 =
  39. 39.359 − 197 =
  40. 40.600 − 198 =

Answer key

  1. 184
  2. 438
  3. 296
  4. 238
  5. 370
  6. 80
  7. 110
  8. 572
  9. 168
  10. 572
  11. 125
  12. 710
  13. 640
  14. 87
  15. 473
  16. 81
  17. 148
  18. 526
  19. 72
  20. 246
  21. 650
  22. 77
  23. 81
  24. 548
  25. 155
  26. 51
  27. 93
  28. 101
  29. 345
  30. 542
  31. 75
  32. 147
  33. 18
  34. 510
  35. 146
  36. 208
  37. 171
  38. 148
  39. 162
  40. 402

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