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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 121 · 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. 1.940 − 798 =
  2. 2.303 − 197 =
  3. 3.861 − 509 =
  4. 4.931 − 579 =
  5. 5.347 − 319 =
  6. 6.638 − 499 =
  7. 7.765 − 339 =
  8. 8.768 − 699 =
  9. 9.466 − 398 =
  10. 10.945 − 799 =
  11. 11.751 − 377 =
  12. 12.434 − 398 =
  13. 13.871 − 799 =
  14. 14.768 − 698 =
  15. 15.613 − 297 =
  16. 16.679 − 408 =
  17. 17.923 − 197 =
  18. 18.344 − 199 =
  19. 19.848 − 797 =
  20. 20.567 − 499 =
  21. 21.790 − 387 =
  22. 22.937 − 399 =
  23. 23.257 − 198 =
  24. 24.808 − 309 =
  25. 25.408 − 367 =
  26. 26.467 − 349 =
  27. 27.927 − 797 =
  28. 28.216 − 169 =
  29. 29.360 − 267 =
  30. 30.678 − 589 =
  31. 31.621 − 497 =
  32. 32.552 − 427 =
  33. 33.599 − 248 =
  34. 34.948 − 388 =
  35. 35.985 − 588 =
  36. 36.554 − 198 =
  37. 37.831 − 598 =
  38. 38.577 − 539 =
  39. 39.913 − 267 =
  40. 40.659 − 539 =

Answer key

  1. 142
  2. 106
  3. 352
  4. 352
  5. 28
  6. 139
  7. 426
  8. 69
  9. 68
  10. 146
  11. 374
  12. 36
  13. 72
  14. 70
  15. 316
  16. 271
  17. 726
  18. 145
  19. 51
  20. 68
  21. 403
  22. 538
  23. 59
  24. 499
  25. 41
  26. 118
  27. 130
  28. 47
  29. 93
  30. 89
  31. 124
  32. 125
  33. 351
  34. 560
  35. 397
  36. 356
  37. 233
  38. 38
  39. 646
  40. 120

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