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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 109 · 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. 1.764 − 597 =
  2. 2.966 − 608 =
  3. 3.670 − 297 =
  4. 4.441 − 399 =
  5. 5.456 − 398 =
  6. 6.967 − 697 =
  7. 7.814 − 399 =
  8. 8.655 − 498 =
  9. 9.790 − 299 =
  10. 10.632 − 388 =
  11. 11.736 − 669 =
  12. 12.441 − 247 =
  13. 13.812 − 399 =
  14. 14.490 − 349 =
  15. 15.806 − 199 =
  16. 16.467 − 287 =
  17. 17.805 − 299 =
  18. 18.474 − 177 =
  19. 19.663 − 627 =
  20. 20.716 − 697 =
  21. 21.847 − 139 =
  22. 22.776 − 699 =
  23. 23.961 − 699 =
  24. 24.576 − 498 =
  25. 25.352 − 197 =
  26. 26.997 − 378 =
  27. 27.708 − 587 =
  28. 28.939 − 149 =
  29. 29.775 − 617 =
  30. 30.298 − 209 =
  31. 31.711 − 507 =
  32. 32.664 − 549 =
  33. 33.701 − 658 =
  34. 34.652 − 599 =
  35. 35.349 − 298 =
  36. 36.622 − 538 =
  37. 37.712 − 197 =
  38. 38.778 − 197 =
  39. 39.431 − 299 =
  40. 40.708 − 477 =

Answer key

  1. 167
  2. 358
  3. 373
  4. 42
  5. 58
  6. 270
  7. 415
  8. 157
  9. 491
  10. 244
  11. 67
  12. 194
  13. 413
  14. 141
  15. 607
  16. 180
  17. 506
  18. 297
  19. 36
  20. 19
  21. 708
  22. 77
  23. 262
  24. 78
  25. 155
  26. 619
  27. 121
  28. 790
  29. 158
  30. 89
  31. 204
  32. 115
  33. 43
  34. 53
  35. 51
  36. 84
  37. 515
  38. 581
  39. 132
  40. 231

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