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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 315 · 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. 1.659 − 397 =
  2. 2.843 − 657 =
  3. 3.942 − 639 =
  4. 4.841 − 199 =
  5. 5.991 − 668 =
  6. 6.631 − 197 =
  7. 7.839 − 157 =
  8. 8.857 − 698 =
  9. 9.837 − 307 =
  10. 10.673 − 498 =
  11. 11.589 − 528 =
  12. 12.807 − 697 =
  13. 13.925 − 299 =
  14. 14.727 − 528 =
  15. 15.571 − 439 =
  16. 16.655 − 368 =
  17. 17.935 − 498 =
  18. 18.515 − 398 =
  19. 19.442 − 297 =
  20. 20.474 − 397 =
  21. 21.758 − 247 =
  22. 22.434 − 299 =
  23. 23.883 − 498 =
  24. 24.655 − 198 =
  25. 25.266 − 177 =
  26. 26.786 − 697 =
  27. 27.918 − 447 =
  28. 28.952 − 798 =
  29. 29.407 − 299 =
  30. 30.666 − 199 =
  31. 31.845 − 488 =
  32. 32.451 − 297 =
  33. 33.951 − 679 =
  34. 34.940 − 198 =
  35. 35.444 − 299 =
  36. 36.328 − 169 =
  37. 37.966 − 299 =
  38. 38.702 − 497 =
  39. 39.932 − 657 =
  40. 40.576 − 298 =

Answer key

  1. 262
  2. 186
  3. 303
  4. 642
  5. 323
  6. 434
  7. 682
  8. 159
  9. 530
  10. 175
  11. 61
  12. 110
  13. 626
  14. 199
  15. 132
  16. 287
  17. 437
  18. 117
  19. 145
  20. 77
  21. 511
  22. 135
  23. 385
  24. 457
  25. 89
  26. 89
  27. 471
  28. 154
  29. 108
  30. 467
  31. 357
  32. 154
  33. 272
  34. 742
  35. 145
  36. 159
  37. 667
  38. 205
  39. 275
  40. 278

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