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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 112 · 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. 1.884 − 397 =
  2. 2.824 − 649 =
  3. 3.595 − 149 =
  4. 4.996 − 799 =
  5. 5.877 − 499 =
  6. 6.423 − 407 =
  7. 7.612 − 259 =
  8. 8.806 − 407 =
  9. 9.959 − 468 =
  10. 10.176 − 158 =
  11. 11.820 − 398 =
  12. 12.548 − 468 =
  13. 13.957 − 398 =
  14. 14.533 − 399 =
  15. 15.161 − 128 =
  16. 16.675 − 399 =
  17. 17.657 − 498 =
  18. 18.880 − 599 =
  19. 19.800 − 697 =
  20. 20.967 − 798 =
  21. 21.662 − 597 =
  22. 22.851 − 797 =
  23. 23.655 − 607 =
  24. 24.666 − 318 =
  25. 25.626 − 477 =
  26. 26.368 − 299 =
  27. 27.980 − 297 =
  28. 28.206 − 128 =
  29. 29.525 − 269 =
  30. 30.912 − 459 =
  31. 31.986 − 497 =
  32. 32.760 − 197 =
  33. 33.350 − 198 =
  34. 34.600 − 497 =
  35. 35.688 − 599 =
  36. 36.446 − 269 =
  37. 37.597 − 299 =
  38. 38.598 − 548 =
  39. 39.619 − 498 =
  40. 40.407 − 178 =

Answer key

  1. 487
  2. 175
  3. 446
  4. 197
  5. 378
  6. 16
  7. 353
  8. 399
  9. 491
  10. 18
  11. 422
  12. 80
  13. 559
  14. 134
  15. 33
  16. 276
  17. 159
  18. 281
  19. 103
  20. 169
  21. 65
  22. 54
  23. 48
  24. 348
  25. 149
  26. 69
  27. 683
  28. 78
  29. 256
  30. 453
  31. 489
  32. 563
  33. 152
  34. 103
  35. 89
  36. 177
  37. 298
  38. 50
  39. 121
  40. 229

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