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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 513 · 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. 1.715 − 599 =
  2. 2.467 − 429 =
  3. 3.642 − 599 =
  4. 4.577 − 499 =
  5. 5.898 − 589 =
  6. 6.422 − 387 =
  7. 7.562 − 409 =
  8. 8.699 − 428 =
  9. 9.947 − 178 =
  10. 10.911 − 579 =
  11. 11.663 − 599 =
  12. 12.348 − 298 =
  13. 13.865 − 598 =
  14. 14.522 − 399 =
  15. 15.770 − 499 =
  16. 16.916 − 797 =
  17. 17.342 − 228 =
  18. 18.909 − 687 =
  19. 19.636 − 597 =
  20. 20.985 − 518 =
  21. 21.945 − 698 =
  22. 22.947 − 298 =
  23. 23.850 − 479 =
  24. 24.871 − 697 =
  25. 25.908 − 299 =
  26. 26.867 − 199 =
  27. 27.439 − 198 =
  28. 28.778 − 497 =
  29. 29.863 − 297 =
  30. 30.160 − 139 =
  31. 31.884 − 197 =
  32. 32.629 − 497 =
  33. 33.913 − 687 =
  34. 34.832 − 799 =
  35. 35.763 − 298 =
  36. 36.944 − 618 =
  37. 37.873 − 699 =
  38. 38.411 − 268 =
  39. 39.708 − 228 =
  40. 40.827 − 798 =

Answer key

  1. 116
  2. 38
  3. 43
  4. 78
  5. 309
  6. 35
  7. 153
  8. 271
  9. 769
  10. 332
  11. 64
  12. 50
  13. 267
  14. 123
  15. 271
  16. 119
  17. 114
  18. 222
  19. 39
  20. 467
  21. 247
  22. 649
  23. 371
  24. 174
  25. 609
  26. 668
  27. 241
  28. 281
  29. 566
  30. 21
  31. 687
  32. 132
  33. 226
  34. 33
  35. 465
  36. 326
  37. 174
  38. 143
  39. 480
  40. 29

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