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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 849 · 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. 1.843 − 479 =
  2. 2.597 − 218 =
  3. 3.244 − 199 =
  4. 4.641 − 599 =
  5. 5.985 − 278 =
  6. 6.685 − 499 =
  7. 7.962 − 399 =
  8. 8.563 − 247 =
  9. 9.654 − 299 =
  10. 10.873 − 599 =
  11. 11.500 − 199 =
  12. 12.319 − 299 =
  13. 13.319 − 157 =
  14. 14.897 − 269 =
  15. 15.987 − 697 =
  16. 16.748 − 599 =
  17. 17.692 − 298 =
  18. 18.408 − 299 =
  19. 19.726 − 599 =
  20. 20.894 − 697 =
  21. 21.844 − 799 =
  22. 22.916 − 599 =
  23. 23.610 − 477 =
  24. 24.910 − 197 =
  25. 25.917 − 598 =
  26. 26.762 − 599 =
  27. 27.683 − 529 =
  28. 28.947 − 159 =
  29. 29.603 − 319 =
  30. 30.979 − 477 =
  31. 31.620 − 367 =
  32. 32.841 − 799 =
  33. 33.934 − 698 =
  34. 34.842 − 799 =
  35. 35.676 − 218 =
  36. 36.830 − 797 =
  37. 37.639 − 198 =
  38. 38.773 − 697 =
  39. 39.936 − 299 =
  40. 40.528 − 499 =

Answer key

  1. 364
  2. 379
  3. 45
  4. 42
  5. 707
  6. 186
  7. 563
  8. 316
  9. 355
  10. 274
  11. 301
  12. 20
  13. 162
  14. 628
  15. 290
  16. 149
  17. 394
  18. 109
  19. 127
  20. 197
  21. 45
  22. 317
  23. 133
  24. 713
  25. 319
  26. 163
  27. 154
  28. 788
  29. 284
  30. 502
  31. 253
  32. 42
  33. 236
  34. 43
  35. 458
  36. 33
  37. 441
  38. 76
  39. 637
  40. 29

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