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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 801 · 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. 1.630 − 599 =
  2. 2.814 − 498 =
  3. 3.737 − 287 =
  4. 4.768 − 298 =
  5. 5.811 − 199 =
  6. 6.635 − 497 =
  7. 7.435 − 398 =
  8. 8.525 − 237 =
  9. 9.798 − 397 =
  10. 10.986 − 197 =
  11. 11.666 − 437 =
  12. 12.764 − 497 =
  13. 13.921 − 799 =
  14. 14.947 − 299 =
  15. 15.641 − 559 =
  16. 16.722 − 169 =
  17. 17.801 − 597 =
  18. 18.625 − 237 =
  19. 19.987 − 198 =
  20. 20.872 − 797 =
  21. 21.628 − 437 =
  22. 22.965 − 597 =
  23. 23.843 − 437 =
  24. 24.884 − 698 =
  25. 25.976 − 539 =
  26. 26.378 − 187 =
  27. 27.624 − 567 =
  28. 28.776 − 628 =
  29. 29.702 − 377 =
  30. 30.910 − 428 =
  31. 31.743 − 698 =
  32. 32.958 − 399 =
  33. 33.628 − 599 =
  34. 34.739 − 398 =
  35. 35.647 − 189 =
  36. 36.858 − 799 =
  37. 37.784 − 599 =
  38. 38.877 − 269 =
  39. 39.833 − 299 =
  40. 40.849 − 497 =

Answer key

  1. 31
  2. 316
  3. 450
  4. 470
  5. 612
  6. 138
  7. 37
  8. 288
  9. 401
  10. 789
  11. 229
  12. 267
  13. 122
  14. 648
  15. 82
  16. 553
  17. 204
  18. 388
  19. 789
  20. 75
  21. 191
  22. 368
  23. 406
  24. 186
  25. 437
  26. 191
  27. 57
  28. 148
  29. 325
  30. 482
  31. 45
  32. 559
  33. 29
  34. 341
  35. 458
  36. 59
  37. 185
  38. 608
  39. 534
  40. 352

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