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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 335 · 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. 1.741 − 167 =
  2. 2.711 − 199 =
  3. 3.843 − 697 =
  4. 4.951 − 498 =
  5. 5.920 − 347 =
  6. 6.696 − 409 =
  7. 7.608 − 497 =
  8. 8.805 − 499 =
  9. 9.726 − 628 =
  10. 10.817 − 297 =
  11. 11.245 − 227 =
  12. 12.437 − 397 =
  13. 13.715 − 399 =
  14. 14.570 − 498 =
  15. 15.558 − 209 =
  16. 16.930 − 397 =
  17. 17.411 − 288 =
  18. 18.812 − 577 =
  19. 19.824 − 298 =
  20. 20.902 − 129 =
  21. 21.882 − 497 =
  22. 22.388 − 119 =
  23. 23.820 − 208 =
  24. 24.420 − 338 =
  25. 25.919 − 698 =
  26. 26.773 − 558 =
  27. 27.515 − 498 =
  28. 28.545 − 397 =
  29. 29.532 − 497 =
  30. 30.416 − 399 =
  31. 31.718 − 497 =
  32. 32.358 − 199 =
  33. 33.165 − 128 =
  34. 34.782 − 399 =
  35. 35.560 − 397 =
  36. 36.432 − 259 =
  37. 37.979 − 449 =
  38. 38.751 − 359 =
  39. 39.786 − 259 =
  40. 40.405 − 197 =

Answer key

  1. 574
  2. 512
  3. 146
  4. 453
  5. 573
  6. 287
  7. 111
  8. 306
  9. 98
  10. 520
  11. 18
  12. 40
  13. 316
  14. 72
  15. 349
  16. 533
  17. 123
  18. 235
  19. 526
  20. 773
  21. 385
  22. 269
  23. 612
  24. 82
  25. 221
  26. 215
  27. 17
  28. 148
  29. 35
  30. 17
  31. 221
  32. 159
  33. 37
  34. 383
  35. 163
  36. 173
  37. 530
  38. 392
  39. 527
  40. 208

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