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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 302 · 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. 1.849 − 459 =
  2. 2.320 − 299 =
  3. 3.495 − 197 =
  4. 4.661 − 507 =
  5. 5.376 − 297 =
  6. 6.850 − 437 =
  7. 7.775 − 297 =
  8. 8.879 − 258 =
  9. 9.567 − 498 =
  10. 10.711 − 197 =
  11. 11.833 − 799 =
  12. 12.801 − 438 =
  13. 13.324 − 259 =
  14. 14.844 − 699 =
  15. 15.892 − 199 =
  16. 16.299 − 199 =
  17. 17.920 − 799 =
  18. 18.402 − 198 =
  19. 19.534 − 497 =
  20. 20.857 − 597 =
  21. 21.743 − 367 =
  22. 22.540 − 317 =
  23. 23.535 − 399 =
  24. 24.925 − 397 =
  25. 25.640 − 198 =
  26. 26.685 − 639 =
  27. 27.883 − 598 =
  28. 28.687 − 599 =
  29. 29.670 − 258 =
  30. 30.964 − 799 =
  31. 31.730 − 699 =
  32. 32.581 − 399 =
  33. 33.843 − 398 =
  34. 34.680 − 397 =
  35. 35.618 − 599 =
  36. 36.824 − 598 =
  37. 37.659 − 197 =
  38. 38.406 − 297 =
  39. 39.359 − 287 =
  40. 40.961 − 797 =

Answer key

  1. 390
  2. 21
  3. 298
  4. 154
  5. 79
  6. 413
  7. 478
  8. 621
  9. 69
  10. 514
  11. 34
  12. 363
  13. 65
  14. 145
  15. 693
  16. 100
  17. 121
  18. 204
  19. 37
  20. 260
  21. 376
  22. 223
  23. 136
  24. 528
  25. 442
  26. 46
  27. 285
  28. 88
  29. 412
  30. 165
  31. 31
  32. 182
  33. 445
  34. 283
  35. 19
  36. 226
  37. 462
  38. 109
  39. 72
  40. 164

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