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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 50 · 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. 1.864 − 397 =
  2. 2.527 − 298 =
  3. 3.942 − 198 =
  4. 4.531 − 399 =
  5. 5.942 − 797 =
  6. 6.356 − 228 =
  7. 7.554 − 288 =
  8. 8.727 − 599 =
  9. 9.639 − 198 =
  10. 10.774 − 438 =
  11. 11.549 − 199 =
  12. 12.603 − 258 =
  13. 13.430 − 298 =
  14. 14.403 − 178 =
  15. 15.428 − 359 =
  16. 16.780 − 659 =
  17. 17.959 − 689 =
  18. 18.888 − 799 =
  19. 19.742 − 599 =
  20. 20.988 − 498 =
  21. 21.441 − 298 =
  22. 22.826 − 198 =
  23. 23.939 − 577 =
  24. 24.841 − 799 =
  25. 25.680 − 299 =
  26. 26.502 − 297 =
  27. 27.536 − 337 =
  28. 28.755 − 669 =
  29. 29.786 − 697 =
  30. 30.309 − 148 =
  31. 31.862 − 698 =
  32. 32.624 − 199 =
  33. 33.380 − 298 =
  34. 34.175 − 157 =
  35. 35.875 − 799 =
  36. 36.339 − 298 =
  37. 37.892 − 508 =
  38. 38.706 − 599 =
  39. 39.617 − 599 =
  40. 40.551 − 139 =

Answer key

  1. 467
  2. 229
  3. 744
  4. 132
  5. 145
  6. 128
  7. 266
  8. 128
  9. 441
  10. 336
  11. 350
  12. 345
  13. 132
  14. 225
  15. 69
  16. 121
  17. 270
  18. 89
  19. 143
  20. 490
  21. 143
  22. 628
  23. 362
  24. 42
  25. 381
  26. 205
  27. 199
  28. 86
  29. 89
  30. 161
  31. 164
  32. 425
  33. 82
  34. 18
  35. 76
  36. 41
  37. 384
  38. 107
  39. 18
  40. 412

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