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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 183 · 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. 1.284 − 129 =
  2. 2.821 − 499 =
  3. 3.999 − 798 =
  4. 4.818 − 798 =
  5. 5.725 − 199 =
  6. 6.961 − 239 =
  7. 7.913 − 798 =
  8. 8.510 − 298 =
  9. 9.339 − 197 =
  10. 10.390 − 199 =
  11. 11.737 − 527 =
  12. 12.673 − 498 =
  13. 13.771 − 198 =
  14. 14.806 − 699 =
  15. 15.343 − 128 =
  16. 16.825 − 598 =
  17. 17.865 − 698 =
  18. 18.897 − 128 =
  19. 19.725 − 157 =
  20. 20.765 − 698 =
  21. 21.530 − 498 =
  22. 22.508 − 469 =
  23. 23.579 − 449 =
  24. 24.523 − 399 =
  25. 25.726 − 288 =
  26. 26.660 − 299 =
  27. 27.815 − 799 =
  28. 28.892 − 559 =
  29. 29.495 − 208 =
  30. 30.643 − 497 =
  31. 31.787 − 697 =
  32. 32.883 − 498 =
  33. 33.394 − 299 =
  34. 34.884 − 698 =
  35. 35.989 − 429 =
  36. 36.438 − 378 =
  37. 37.736 − 547 =
  38. 38.276 − 197 =
  39. 39.440 − 318 =
  40. 40.606 − 497 =

Answer key

  1. 155
  2. 322
  3. 201
  4. 20
  5. 526
  6. 722
  7. 115
  8. 212
  9. 142
  10. 191
  11. 210
  12. 175
  13. 573
  14. 107
  15. 215
  16. 227
  17. 167
  18. 769
  19. 568
  20. 67
  21. 32
  22. 39
  23. 130
  24. 124
  25. 438
  26. 361
  27. 16
  28. 333
  29. 287
  30. 146
  31. 90
  32. 385
  33. 95
  34. 186
  35. 560
  36. 60
  37. 189
  38. 79
  39. 122
  40. 109

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