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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 379 · 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. 1.548 − 417 =
  2. 2.880 − 358 =
  3. 3.716 − 599 =
  4. 4.933 − 577 =
  5. 5.866 − 639 =
  6. 6.998 − 798 =
  7. 7.684 − 399 =
  8. 8.782 − 467 =
  9. 9.726 − 298 =
  10. 10.688 − 399 =
  11. 11.666 − 637 =
  12. 12.691 − 349 =
  13. 13.984 − 799 =
  14. 14.952 − 148 =
  15. 15.361 − 197 =
  16. 16.421 − 299 =
  17. 17.341 − 259 =
  18. 18.886 − 497 =
  19. 19.995 − 607 =
  20. 20.992 − 597 =
  21. 21.829 − 197 =
  22. 22.696 − 347 =
  23. 23.862 − 799 =
  24. 24.855 − 697 =
  25. 25.565 − 297 =
  26. 26.771 − 498 =
  27. 27.492 − 297 =
  28. 28.882 − 277 =
  29. 29.701 − 219 =
  30. 30.919 − 638 =
  31. 31.923 − 659 =
  32. 32.494 − 437 =
  33. 33.672 − 577 =
  34. 34.807 − 677 =
  35. 35.931 − 619 =
  36. 36.899 − 499 =
  37. 37.816 − 699 =
  38. 38.532 − 299 =
  39. 39.729 − 257 =
  40. 40.759 − 217 =

Answer key

  1. 131
  2. 522
  3. 117
  4. 356
  5. 227
  6. 200
  7. 285
  8. 315
  9. 428
  10. 289
  11. 29
  12. 342
  13. 185
  14. 804
  15. 164
  16. 122
  17. 82
  18. 389
  19. 388
  20. 395
  21. 632
  22. 349
  23. 63
  24. 158
  25. 268
  26. 273
  27. 195
  28. 605
  29. 482
  30. 281
  31. 264
  32. 57
  33. 95
  34. 130
  35. 312
  36. 400
  37. 117
  38. 233
  39. 472
  40. 542

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