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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 400 · 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. 1.769 − 697 =
  2. 2.747 − 199 =
  3. 3.693 − 518 =
  4. 4.266 − 248 =
  5. 5.891 − 498 =
  6. 6.825 − 399 =
  7. 7.930 − 599 =
  8. 8.762 − 597 =
  9. 9.857 − 488 =
  10. 10.595 − 397 =
  11. 11.800 − 497 =
  12. 12.836 − 379 =
  13. 13.867 − 798 =
  14. 14.762 − 598 =
  15. 15.872 − 479 =
  16. 16.518 − 178 =
  17. 17.333 − 169 =
  18. 18.197 − 178 =
  19. 19.779 − 489 =
  20. 20.509 − 247 =
  21. 21.657 − 599 =
  22. 22.714 − 409 =
  23. 23.224 − 199 =
  24. 24.410 − 297 =
  25. 25.665 − 598 =
  26. 26.321 − 298 =
  27. 27.902 − 678 =
  28. 28.323 − 207 =
  29. 29.301 − 269 =
  30. 30.809 − 697 =
  31. 31.756 − 499 =
  32. 32.876 − 659 =
  33. 33.855 − 797 =
  34. 34.525 − 497 =
  35. 35.421 − 388 =
  36. 36.500 − 297 =
  37. 37.822 − 799 =
  38. 38.903 − 797 =
  39. 39.840 − 698 =
  40. 40.811 − 298 =

Answer key

  1. 72
  2. 548
  3. 175
  4. 18
  5. 393
  6. 426
  7. 331
  8. 165
  9. 369
  10. 198
  11. 303
  12. 457
  13. 69
  14. 164
  15. 393
  16. 340
  17. 164
  18. 19
  19. 290
  20. 262
  21. 58
  22. 305
  23. 25
  24. 113
  25. 67
  26. 23
  27. 224
  28. 116
  29. 32
  30. 112
  31. 257
  32. 217
  33. 58
  34. 28
  35. 33
  36. 203
  37. 23
  38. 106
  39. 142
  40. 513

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