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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 965 · 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. 1.554 − 159 =
  2. 2.521 − 299 =
  3. 3.862 − 399 =
  4. 4.681 − 409 =
  5. 5.777 − 688 =
  6. 6.658 − 197 =
  7. 7.935 − 598 =
  8. 8.614 − 568 =
  9. 9.930 − 399 =
  10. 10.888 − 797 =
  11. 11.946 − 697 =
  12. 12.645 − 617 =
  13. 13.974 − 668 =
  14. 14.549 − 197 =
  15. 15.678 − 178 =
  16. 16.923 − 697 =
  17. 17.335 − 298 =
  18. 18.295 − 199 =
  19. 19.507 − 398 =
  20. 20.550 − 497 =
  21. 21.453 − 249 =
  22. 22.744 − 169 =
  23. 23.588 − 379 =
  24. 24.889 − 309 =
  25. 25.861 − 197 =
  26. 26.649 − 577 =
  27. 27.614 − 427 =
  28. 28.703 − 599 =
  29. 29.585 − 129 =
  30. 30.860 − 598 =
  31. 31.923 − 199 =
  32. 32.534 − 199 =
  33. 33.972 − 398 =
  34. 34.701 − 587 =
  35. 35.900 − 529 =
  36. 36.987 − 678 =
  37. 37.677 − 579 =
  38. 38.944 − 268 =
  39. 39.454 − 398 =
  40. 40.659 − 398 =

Answer key

  1. 395
  2. 222
  3. 463
  4. 272
  5. 89
  6. 461
  7. 337
  8. 46
  9. 531
  10. 91
  11. 249
  12. 28
  13. 306
  14. 352
  15. 500
  16. 226
  17. 37
  18. 96
  19. 109
  20. 53
  21. 204
  22. 575
  23. 209
  24. 580
  25. 664
  26. 72
  27. 187
  28. 104
  29. 456
  30. 262
  31. 724
  32. 335
  33. 574
  34. 114
  35. 371
  36. 309
  37. 98
  38. 676
  39. 56
  40. 261

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