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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 862 · 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. 1.990 − 417 =
  2. 2.526 − 449 =
  3. 3.682 − 489 =
  4. 4.911 − 797 =
  5. 5.654 − 599 =
  6. 6.877 − 799 =
  7. 7.604 − 257 =
  8. 8.935 − 798 =
  9. 9.946 − 687 =
  10. 10.928 − 697 =
  11. 11.931 − 798 =
  12. 12.719 − 399 =
  13. 13.391 − 298 =
  14. 14.590 − 339 =
  15. 15.706 − 657 =
  16. 16.598 − 459 =
  17. 17.634 − 529 =
  18. 18.923 − 797 =
  19. 19.212 − 157 =
  20. 20.832 − 117 =
  21. 21.616 − 599 =
  22. 22.784 − 399 =
  23. 23.597 − 399 =
  24. 24.768 − 518 =
  25. 25.624 − 467 =
  26. 26.662 − 497 =
  27. 27.498 − 449 =
  28. 28.933 − 799 =
  29. 29.748 − 598 =
  30. 30.956 − 517 =
  31. 31.847 − 498 =
  32. 32.730 − 397 =
  33. 33.816 − 797 =
  34. 34.196 − 148 =
  35. 35.954 − 698 =
  36. 36.742 − 398 =
  37. 37.868 − 659 =
  38. 38.320 − 297 =
  39. 39.839 − 599 =
  40. 40.547 − 198 =

Answer key

  1. 573
  2. 77
  3. 193
  4. 114
  5. 55
  6. 78
  7. 347
  8. 137
  9. 259
  10. 231
  11. 133
  12. 320
  13. 93
  14. 251
  15. 49
  16. 139
  17. 105
  18. 126
  19. 55
  20. 715
  21. 17
  22. 385
  23. 198
  24. 250
  25. 157
  26. 165
  27. 49
  28. 134
  29. 150
  30. 439
  31. 349
  32. 333
  33. 19
  34. 48
  35. 256
  36. 344
  37. 209
  38. 23
  39. 240
  40. 349

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