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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 474 · 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. 1.640 − 497 =
  2. 2.859 − 797 =
  3. 3.870 − 298 =
  4. 4.868 − 498 =
  5. 5.321 − 179 =
  6. 6.307 − 269 =
  7. 7.409 − 297 =
  8. 8.666 − 499 =
  9. 9.967 − 799 =
  10. 10.667 − 618 =
  11. 11.724 − 207 =
  12. 12.640 − 597 =
  13. 13.815 − 498 =
  14. 14.710 − 499 =
  15. 15.732 − 687 =
  16. 16.497 − 347 =
  17. 17.857 − 498 =
  18. 18.947 − 438 =
  19. 19.677 − 489 =
  20. 20.867 − 629 =
  21. 21.272 − 168 =
  22. 22.291 − 258 =
  23. 23.828 − 297 =
  24. 24.907 − 399 =
  25. 25.930 − 697 =
  26. 26.731 − 648 =
  27. 27.968 − 399 =
  28. 28.806 − 697 =
  29. 29.474 − 309 =
  30. 30.940 − 399 =
  31. 31.857 − 597 =
  32. 32.187 − 119 =
  33. 33.663 − 147 =
  34. 34.769 − 697 =
  35. 35.708 − 349 =
  36. 36.966 − 199 =
  37. 37.961 − 479 =
  38. 38.500 − 299 =
  39. 39.600 − 457 =
  40. 40.385 − 297 =

Answer key

  1. 143
  2. 62
  3. 572
  4. 370
  5. 142
  6. 38
  7. 112
  8. 167
  9. 168
  10. 49
  11. 517
  12. 43
  13. 317
  14. 211
  15. 45
  16. 150
  17. 359
  18. 509
  19. 188
  20. 238
  21. 104
  22. 33
  23. 531
  24. 508
  25. 233
  26. 83
  27. 569
  28. 109
  29. 165
  30. 541
  31. 260
  32. 68
  33. 516
  34. 72
  35. 359
  36. 767
  37. 482
  38. 201
  39. 143
  40. 88

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