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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 74 · 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. 1.771 − 657 =
  2. 2.779 − 677 =
  3. 3.693 − 599 =
  4. 4.898 − 697 =
  5. 5.771 − 297 =
  6. 6.926 − 298 =
  7. 7.880 − 799 =
  8. 8.865 − 499 =
  9. 9.718 − 198 =
  10. 10.609 − 498 =
  11. 11.976 − 698 =
  12. 12.699 − 468 =
  13. 13.612 − 518 =
  14. 14.485 − 149 =
  15. 15.596 − 469 =
  16. 16.701 − 189 =
  17. 17.721 − 597 =
  18. 18.523 − 197 =
  19. 19.371 − 338 =
  20. 20.280 − 168 =
  21. 21.368 − 299 =
  22. 22.797 − 697 =
  23. 23.865 − 429 =
  24. 24.346 − 117 =
  25. 25.485 − 399 =
  26. 26.837 − 559 =
  27. 27.604 − 559 =
  28. 28.761 − 548 =
  29. 29.971 − 698 =
  30. 30.737 − 497 =
  31. 31.410 − 298 =
  32. 32.648 − 259 =
  33. 33.587 − 398 =
  34. 34.428 − 298 =
  35. 35.855 − 289 =
  36. 36.426 − 409 =
  37. 37.825 − 697 =
  38. 38.553 − 498 =
  39. 39.812 − 578 =
  40. 40.982 − 798 =

Answer key

  1. 114
  2. 102
  3. 94
  4. 201
  5. 474
  6. 628
  7. 81
  8. 366
  9. 520
  10. 111
  11. 278
  12. 231
  13. 94
  14. 336
  15. 127
  16. 512
  17. 124
  18. 326
  19. 33
  20. 112
  21. 69
  22. 100
  23. 436
  24. 229
  25. 86
  26. 278
  27. 45
  28. 213
  29. 273
  30. 240
  31. 112
  32. 389
  33. 189
  34. 130
  35. 566
  36. 17
  37. 128
  38. 55
  39. 234
  40. 184

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