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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 526 · 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. 1.678 − 647 =
  2. 2.786 − 677 =
  3. 3.759 − 398 =
  4. 4.842 − 598 =
  5. 5.771 − 499 =
  6. 6.876 − 278 =
  7. 7.470 − 427 =
  8. 8.845 − 197 =
  9. 9.611 − 149 =
  10. 10.943 − 287 =
  11. 11.976 − 197 =
  12. 12.770 − 698 =
  13. 13.589 − 397 =
  14. 14.712 − 597 =
  15. 15.349 − 307 =
  16. 16.501 − 208 =
  17. 17.989 − 149 =
  18. 18.939 − 469 =
  19. 19.864 − 597 =
  20. 20.630 − 197 =
  21. 21.325 − 298 =
  22. 22.181 − 118 =
  23. 23.837 − 659 =
  24. 24.898 − 197 =
  25. 25.668 − 599 =
  26. 26.248 − 198 =
  27. 27.757 − 199 =
  28. 28.782 − 499 =
  29. 29.990 − 497 =
  30. 30.611 − 498 =
  31. 31.898 − 458 =
  32. 32.760 − 699 =
  33. 33.783 − 298 =
  34. 34.545 − 498 =
  35. 35.824 − 298 =
  36. 36.839 − 698 =
  37. 37.819 − 799 =
  38. 38.454 − 197 =
  39. 39.237 − 197 =
  40. 40.311 − 149 =

Answer key

  1. 31
  2. 109
  3. 361
  4. 244
  5. 272
  6. 598
  7. 43
  8. 648
  9. 462
  10. 656
  11. 779
  12. 72
  13. 192
  14. 115
  15. 42
  16. 293
  17. 840
  18. 470
  19. 267
  20. 433
  21. 27
  22. 63
  23. 178
  24. 701
  25. 69
  26. 50
  27. 558
  28. 283
  29. 493
  30. 113
  31. 440
  32. 61
  33. 485
  34. 47
  35. 526
  36. 141
  37. 20
  38. 257
  39. 40
  40. 162

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