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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 915 · 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. 1.616 − 397 =
  2. 2.632 − 229 =
  3. 3.811 − 599 =
  4. 4.971 − 399 =
  5. 5.774 − 637 =
  6. 6.214 − 158 =
  7. 7.554 − 399 =
  8. 8.887 − 698 =
  9. 9.327 − 199 =
  10. 10.760 − 699 =
  11. 11.370 − 339 =
  12. 12.860 − 599 =
  13. 13.422 − 178 =
  14. 14.499 − 367 =
  15. 15.824 − 797 =
  16. 16.345 − 299 =
  17. 17.543 − 397 =
  18. 18.343 − 298 =
  19. 19.668 − 399 =
  20. 20.888 − 499 =
  21. 21.930 − 799 =
  22. 22.634 − 597 =
  23. 23.560 − 478 =
  24. 24.668 − 498 =
  25. 25.920 − 598 =
  26. 26.360 − 198 =
  27. 27.450 − 189 =
  28. 28.942 − 698 =
  29. 29.972 − 798 =
  30. 30.498 − 398 =
  31. 31.600 − 297 =
  32. 32.848 − 567 =
  33. 33.571 − 227 =
  34. 34.446 − 199 =
  35. 35.897 − 399 =
  36. 36.742 − 237 =
  37. 37.541 − 497 =
  38. 38.963 − 598 =
  39. 39.698 − 199 =
  40. 40.474 − 399 =

Answer key

  1. 219
  2. 403
  3. 212
  4. 572
  5. 137
  6. 56
  7. 155
  8. 189
  9. 128
  10. 61
  11. 31
  12. 261
  13. 244
  14. 132
  15. 27
  16. 46
  17. 146
  18. 45
  19. 269
  20. 389
  21. 131
  22. 37
  23. 82
  24. 170
  25. 322
  26. 162
  27. 261
  28. 244
  29. 174
  30. 100
  31. 303
  32. 281
  33. 344
  34. 247
  35. 498
  36. 505
  37. 44
  38. 365
  39. 499
  40. 75

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