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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 447 · 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. 1.831 − 287 =
  2. 2.766 − 208 =
  3. 3.868 − 497 =
  4. 4.612 − 599 =
  5. 5.904 − 247 =
  6. 6.493 − 199 =
  7. 7.554 − 498 =
  8. 8.706 − 597 =
  9. 9.581 − 298 =
  10. 10.707 − 629 =
  11. 11.719 − 397 =
  12. 12.897 − 599 =
  13. 13.494 − 469 =
  14. 14.829 − 798 =
  15. 15.638 − 568 =
  16. 16.994 − 198 =
  17. 17.964 − 428 =
  18. 18.805 − 697 =
  19. 19.702 − 659 =
  20. 20.880 − 399 =
  21. 21.446 − 399 =
  22. 22.565 − 419 =
  23. 23.756 − 399 =
  24. 24.359 − 218 =
  25. 25.887 − 497 =
  26. 26.614 − 288 =
  27. 27.330 − 219 =
  28. 28.362 − 149 =
  29. 29.534 − 137 =
  30. 30.519 − 197 =
  31. 31.698 − 598 =
  32. 32.758 − 199 =
  33. 33.763 − 178 =
  34. 34.691 − 198 =
  35. 35.856 − 797 =
  36. 36.529 − 499 =
  37. 37.856 − 699 =
  38. 38.449 − 298 =
  39. 39.355 − 119 =
  40. 40.576 − 509 =

Answer key

  1. 544
  2. 558
  3. 371
  4. 13
  5. 657
  6. 294
  7. 56
  8. 109
  9. 283
  10. 78
  11. 322
  12. 298
  13. 25
  14. 31
  15. 70
  16. 796
  17. 536
  18. 108
  19. 43
  20. 481
  21. 47
  22. 146
  23. 357
  24. 141
  25. 390
  26. 326
  27. 111
  28. 213
  29. 397
  30. 322
  31. 100
  32. 559
  33. 585
  34. 493
  35. 59
  36. 30
  37. 157
  38. 151
  39. 236
  40. 67

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