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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 440 · 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. 1.968 − 798 =
  2. 2.455 − 337 =
  3. 3.657 − 198 =
  4. 4.746 − 629 =
  5. 5.848 − 619 =
  6. 6.248 − 198 =
  7. 7.528 − 497 =
  8. 8.705 − 607 =
  9. 9.691 − 597 =
  10. 10.675 − 519 =
  11. 11.839 − 499 =
  12. 12.833 − 518 =
  13. 13.848 − 218 =
  14. 14.830 − 407 =
  15. 15.958 − 558 =
  16. 16.608 − 199 =
  17. 17.890 − 797 =
  18. 18.913 − 799 =
  19. 19.674 − 399 =
  20. 20.978 − 639 =
  21. 21.568 − 497 =
  22. 22.369 − 319 =
  23. 23.835 − 497 =
  24. 24.989 − 499 =
  25. 25.776 − 697 =
  26. 26.847 − 128 =
  27. 27.900 − 399 =
  28. 28.823 − 397 =
  29. 29.558 − 509 =
  30. 30.872 − 198 =
  31. 31.538 − 119 =
  32. 32.354 − 297 =
  33. 33.601 − 297 =
  34. 34.865 − 397 =
  35. 35.796 − 347 =
  36. 36.653 − 459 =
  37. 37.533 − 237 =
  38. 38.304 − 187 =
  39. 39.450 − 179 =
  40. 40.943 − 399 =

Answer key

  1. 170
  2. 118
  3. 459
  4. 117
  5. 229
  6. 50
  7. 31
  8. 98
  9. 94
  10. 156
  11. 340
  12. 315
  13. 630
  14. 423
  15. 400
  16. 409
  17. 93
  18. 114
  19. 275
  20. 339
  21. 71
  22. 50
  23. 338
  24. 490
  25. 79
  26. 719
  27. 501
  28. 426
  29. 49
  30. 674
  31. 419
  32. 57
  33. 304
  34. 468
  35. 449
  36. 194
  37. 296
  38. 117
  39. 271
  40. 544

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