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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 239 · 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. 1.524 − 469 =
  2. 2.843 − 237 =
  3. 3.569 − 509 =
  4. 4.933 − 469 =
  5. 5.770 − 298 =
  6. 6.717 − 599 =
  7. 7.857 − 397 =
  8. 8.902 − 337 =
  9. 9.774 − 469 =
  10. 10.890 − 599 =
  11. 11.448 − 398 =
  12. 12.749 − 478 =
  13. 13.895 − 297 =
  14. 14.818 − 198 =
  15. 15.598 − 518 =
  16. 16.453 − 299 =
  17. 17.909 − 699 =
  18. 18.994 − 798 =
  19. 19.753 − 678 =
  20. 20.882 − 299 =
  21. 21.708 − 598 =
  22. 22.655 − 499 =
  23. 23.939 − 697 =
  24. 24.611 − 498 =
  25. 25.674 − 537 =
  26. 26.364 − 197 =
  27. 27.525 − 498 =
  28. 28.368 − 129 =
  29. 29.506 − 259 =
  30. 30.458 − 399 =
  31. 31.341 − 197 =
  32. 32.673 − 139 =
  33. 33.643 − 469 =
  34. 34.689 − 288 =
  35. 35.781 − 699 =
  36. 36.993 − 199 =
  37. 37.465 − 299 =
  38. 38.769 − 259 =
  39. 39.715 − 657 =
  40. 40.570 − 197 =

Answer key

  1. 55
  2. 606
  3. 60
  4. 464
  5. 472
  6. 118
  7. 460
  8. 565
  9. 305
  10. 291
  11. 50
  12. 271
  13. 598
  14. 620
  15. 80
  16. 154
  17. 210
  18. 196
  19. 75
  20. 583
  21. 110
  22. 156
  23. 242
  24. 113
  25. 137
  26. 167
  27. 27
  28. 239
  29. 247
  30. 59
  31. 144
  32. 534
  33. 174
  34. 401
  35. 82
  36. 794
  37. 166
  38. 510
  39. 58
  40. 373

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