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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 386 · 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. 1.831 − 698 =
  2. 2.673 − 597 =
  3. 3.755 − 598 =
  4. 4.205 − 118 =
  5. 5.754 − 357 =
  6. 6.523 − 247 =
  7. 7.624 − 399 =
  8. 8.726 − 398 =
  9. 9.392 − 199 =
  10. 10.447 − 278 =
  11. 11.476 − 428 =
  12. 12.735 − 247 =
  13. 13.515 − 397 =
  14. 14.719 − 408 =
  15. 15.371 − 198 =
  16. 16.229 − 189 =
  17. 17.670 − 508 =
  18. 18.918 − 457 =
  19. 19.524 − 307 =
  20. 20.838 − 799 =
  21. 21.754 − 608 =
  22. 22.376 − 169 =
  23. 23.783 − 598 =
  24. 24.551 − 499 =
  25. 25.728 − 698 =
  26. 26.895 − 799 =
  27. 27.425 − 208 =
  28. 28.817 − 698 =
  29. 29.285 − 197 =
  30. 30.680 − 599 =
  31. 31.614 − 417 =
  32. 32.466 − 418 =
  33. 33.761 − 408 =
  34. 34.731 − 198 =
  35. 35.717 − 319 =
  36. 36.495 − 297 =
  37. 37.522 − 488 =
  38. 38.324 − 289 =
  39. 39.688 − 157 =
  40. 40.843 − 798 =

Answer key

  1. 133
  2. 76
  3. 157
  4. 87
  5. 397
  6. 276
  7. 225
  8. 328
  9. 193
  10. 169
  11. 48
  12. 488
  13. 118
  14. 311
  15. 173
  16. 40
  17. 162
  18. 461
  19. 217
  20. 39
  21. 146
  22. 207
  23. 185
  24. 52
  25. 30
  26. 96
  27. 217
  28. 119
  29. 88
  30. 81
  31. 197
  32. 48
  33. 353
  34. 533
  35. 398
  36. 198
  37. 34
  38. 35
  39. 531
  40. 45

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