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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 710 · 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. 1.922 − 797 =
  2. 2.311 − 167 =
  3. 3.529 − 398 =
  4. 4.676 − 629 =
  5. 5.918 − 299 =
  6. 6.802 − 397 =
  7. 7.844 − 797 =
  8. 8.831 − 299 =
  9. 9.615 − 467 =
  10. 10.864 − 797 =
  11. 11.875 − 699 =
  12. 12.790 − 697 =
  13. 13.998 − 217 =
  14. 14.822 − 539 =
  15. 15.578 − 499 =
  16. 16.801 − 698 =
  17. 17.598 − 498 =
  18. 18.638 − 597 =
  19. 19.945 − 298 =
  20. 20.491 − 257 =
  21. 21.884 − 277 =
  22. 22.948 − 397 =
  23. 23.832 − 207 =
  24. 24.762 − 499 =
  25. 25.712 − 598 =
  26. 26.999 − 699 =
  27. 27.326 − 199 =
  28. 28.812 − 498 =
  29. 29.672 − 149 =
  30. 30.984 − 567 =
  31. 31.599 − 408 =
  32. 32.824 − 629 =
  33. 33.581 − 499 =
  34. 34.646 − 567 =
  35. 35.971 − 698 =
  36. 36.357 − 239 =
  37. 37.333 − 317 =
  38. 38.324 − 279 =
  39. 39.596 − 178 =
  40. 40.658 − 319 =

Answer key

  1. 125
  2. 144
  3. 131
  4. 47
  5. 619
  6. 405
  7. 47
  8. 532
  9. 148
  10. 67
  11. 176
  12. 93
  13. 781
  14. 283
  15. 79
  16. 103
  17. 100
  18. 41
  19. 647
  20. 234
  21. 607
  22. 551
  23. 625
  24. 263
  25. 114
  26. 300
  27. 127
  28. 314
  29. 523
  30. 417
  31. 191
  32. 195
  33. 82
  34. 79
  35. 273
  36. 118
  37. 16
  38. 45
  39. 418
  40. 339

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