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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 390 · 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. 1.605 − 197 =
  2. 2.496 − 479 =
  3. 3.756 − 697 =
  4. 4.583 − 249 =
  5. 5.870 − 397 =
  6. 6.879 − 667 =
  7. 7.889 − 797 =
  8. 8.925 − 467 =
  9. 9.703 − 619 =
  10. 10.671 − 527 =
  11. 11.919 − 408 =
  12. 12.424 − 308 =
  13. 13.577 − 368 =
  14. 14.996 − 598 =
  15. 15.777 − 699 =
  16. 16.832 − 249 =
  17. 17.847 − 798 =
  18. 18.476 − 399 =
  19. 19.907 − 199 =
  20. 20.802 − 159 =
  21. 21.534 − 397 =
  22. 22.889 − 678 =
  23. 23.903 − 408 =
  24. 24.921 − 699 =
  25. 25.782 − 699 =
  26. 26.831 − 497 =
  27. 27.565 − 499 =
  28. 28.390 − 198 =
  29. 29.287 − 198 =
  30. 30.745 − 198 =
  31. 31.328 − 199 =
  32. 32.660 − 608 =
  33. 33.693 − 598 =
  34. 34.848 − 199 =
  35. 35.714 − 699 =
  36. 36.919 − 157 =
  37. 37.588 − 499 =
  38. 38.659 − 199 =
  39. 39.951 − 399 =
  40. 40.963 − 538 =

Answer key

  1. 408
  2. 17
  3. 59
  4. 334
  5. 473
  6. 212
  7. 92
  8. 458
  9. 84
  10. 144
  11. 511
  12. 116
  13. 209
  14. 398
  15. 78
  16. 583
  17. 49
  18. 77
  19. 708
  20. 643
  21. 137
  22. 211
  23. 495
  24. 222
  25. 83
  26. 334
  27. 66
  28. 192
  29. 89
  30. 547
  31. 129
  32. 52
  33. 95
  34. 649
  35. 15
  36. 762
  37. 89
  38. 460
  39. 552
  40. 425

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