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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 234 · 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. 1.419 − 299 =
  2. 2.480 − 369 =
  3. 3.491 − 398 =
  4. 4.745 − 407 =
  5. 5.343 − 207 =
  6. 6.648 − 599 =
  7. 7.901 − 799 =
  8. 8.420 − 188 =
  9. 9.787 − 398 =
  10. 10.356 − 188 =
  11. 11.937 − 498 =
  12. 12.878 − 237 =
  13. 13.577 − 558 =
  14. 14.611 − 207 =
  15. 15.996 − 699 =
  16. 16.885 − 298 =
  17. 17.976 − 689 =
  18. 18.447 − 399 =
  19. 19.779 − 588 =
  20. 20.530 − 397 =
  21. 21.503 − 219 =
  22. 22.935 − 298 =
  23. 23.988 − 509 =
  24. 24.366 − 299 =
  25. 25.263 − 199 =
  26. 26.549 − 379 =
  27. 27.299 − 199 =
  28. 28.502 − 279 =
  29. 29.730 − 699 =
  30. 30.750 − 197 =
  31. 31.317 − 297 =
  32. 32.712 − 599 =
  33. 33.618 − 398 =
  34. 34.504 − 439 =
  35. 35.977 − 297 =
  36. 36.749 − 247 =
  37. 37.870 − 647 =
  38. 38.782 − 399 =
  39. 39.292 − 118 =
  40. 40.905 − 457 =

Answer key

  1. 120
  2. 111
  3. 93
  4. 338
  5. 136
  6. 49
  7. 102
  8. 232
  9. 389
  10. 168
  11. 439
  12. 641
  13. 19
  14. 404
  15. 297
  16. 587
  17. 287
  18. 48
  19. 191
  20. 133
  21. 284
  22. 637
  23. 479
  24. 67
  25. 64
  26. 170
  27. 100
  28. 223
  29. 31
  30. 553
  31. 20
  32. 113
  33. 220
  34. 65
  35. 680
  36. 502
  37. 223
  38. 383
  39. 174
  40. 448

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