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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 375 · 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. 1.587 − 297 =
  2. 2.667 − 427 =
  3. 3.350 − 299 =
  4. 4.757 − 267 =
  5. 5.677 − 649 =
  6. 6.359 − 327 =
  7. 7.669 − 599 =
  8. 8.871 − 798 =
  9. 9.821 − 799 =
  10. 10.955 − 168 =
  11. 11.638 − 198 =
  12. 12.584 − 499 =
  13. 13.548 − 297 =
  14. 14.404 − 299 =
  15. 15.942 − 117 =
  16. 16.626 − 209 =
  17. 17.171 − 119 =
  18. 18.974 − 607 =
  19. 19.250 − 179 =
  20. 20.851 − 319 =
  21. 21.766 − 699 =
  22. 22.959 − 799 =
  23. 23.909 − 799 =
  24. 24.621 − 318 =
  25. 25.467 − 367 =
  26. 26.631 − 187 =
  27. 27.663 − 419 =
  28. 28.297 − 197 =
  29. 29.788 − 597 =
  30. 30.581 − 399 =
  31. 31.232 − 197 =
  32. 32.926 − 597 =
  33. 33.961 − 598 =
  34. 34.917 − 198 =
  35. 35.421 − 349 =
  36. 36.853 − 649 =
  37. 37.827 − 409 =
  38. 38.410 − 267 =
  39. 39.747 − 598 =
  40. 40.963 − 498 =

Answer key

  1. 290
  2. 240
  3. 51
  4. 490
  5. 28
  6. 32
  7. 70
  8. 73
  9. 22
  10. 787
  11. 440
  12. 85
  13. 251
  14. 105
  15. 825
  16. 417
  17. 52
  18. 367
  19. 71
  20. 532
  21. 67
  22. 160
  23. 110
  24. 303
  25. 100
  26. 444
  27. 244
  28. 100
  29. 191
  30. 182
  31. 35
  32. 329
  33. 363
  34. 719
  35. 72
  36. 204
  37. 418
  38. 143
  39. 149
  40. 465

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