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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 438 · 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. 1.536 − 198 =
  2. 2.550 − 198 =
  3. 3.818 − 397 =
  4. 4.666 − 258 =
  5. 5.943 − 799 =
  6. 6.584 − 499 =
  7. 7.780 − 419 =
  8. 8.255 − 167 =
  9. 9.911 − 698 =
  10. 10.861 − 699 =
  11. 11.753 − 698 =
  12. 12.638 − 539 =
  13. 13.784 − 698 =
  14. 14.460 − 397 =
  15. 15.499 − 199 =
  16. 16.785 − 657 =
  17. 17.498 − 437 =
  18. 18.989 − 149 =
  19. 19.849 − 298 =
  20. 20.997 − 597 =
  21. 21.316 − 197 =
  22. 22.730 − 597 =
  23. 23.706 − 649 =
  24. 24.719 − 699 =
  25. 25.706 − 597 =
  26. 26.627 − 398 =
  27. 27.814 − 549 =
  28. 28.864 − 299 =
  29. 29.456 − 159 =
  30. 30.995 − 698 =
  31. 31.937 − 667 =
  32. 32.650 − 499 =
  33. 33.593 − 297 =
  34. 34.428 − 198 =
  35. 35.486 − 299 =
  36. 36.721 − 598 =
  37. 37.278 − 129 =
  38. 38.336 − 299 =
  39. 39.916 − 198 =
  40. 40.497 − 278 =

Answer key

  1. 338
  2. 352
  3. 421
  4. 408
  5. 144
  6. 85
  7. 361
  8. 88
  9. 213
  10. 162
  11. 55
  12. 99
  13. 86
  14. 63
  15. 300
  16. 128
  17. 61
  18. 840
  19. 551
  20. 400
  21. 119
  22. 133
  23. 57
  24. 20
  25. 109
  26. 229
  27. 265
  28. 565
  29. 297
  30. 297
  31. 270
  32. 151
  33. 296
  34. 230
  35. 187
  36. 123
  37. 149
  38. 37
  39. 718
  40. 219

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