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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 359 · 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. 1.866 − 797 =
  2. 2.829 − 598 =
  3. 3.728 − 498 =
  4. 4.552 − 299 =
  5. 5.608 − 279 =
  6. 6.775 − 698 =
  7. 7.817 − 197 =
  8. 8.993 − 799 =
  9. 9.602 − 477 =
  10. 10.882 − 517 =
  11. 11.852 − 299 =
  12. 12.713 − 377 =
  13. 13.944 − 599 =
  14. 14.514 − 299 =
  15. 15.932 − 697 =
  16. 16.687 − 347 =
  17. 17.444 − 299 =
  18. 18.962 − 609 =
  19. 19.685 − 527 =
  20. 20.734 − 679 =
  21. 21.994 − 599 =
  22. 22.432 − 397 =
  23. 23.281 − 197 =
  24. 24.686 − 437 =
  25. 25.847 − 797 =
  26. 26.857 − 689 =
  27. 27.732 − 499 =
  28. 28.939 − 529 =
  29. 29.299 − 199 =
  30. 30.886 − 698 =
  31. 31.798 − 128 =
  32. 32.893 − 498 =
  33. 33.285 − 197 =
  34. 34.635 − 197 =
  35. 35.806 − 697 =
  36. 36.864 − 499 =
  37. 37.878 − 697 =
  38. 38.637 − 299 =
  39. 39.995 − 697 =
  40. 40.245 − 198 =

Answer key

  1. 69
  2. 231
  3. 230
  4. 253
  5. 329
  6. 77
  7. 620
  8. 194
  9. 125
  10. 365
  11. 553
  12. 336
  13. 345
  14. 215
  15. 235
  16. 340
  17. 145
  18. 353
  19. 158
  20. 55
  21. 395
  22. 35
  23. 84
  24. 249
  25. 50
  26. 168
  27. 233
  28. 410
  29. 100
  30. 188
  31. 670
  32. 395
  33. 88
  34. 438
  35. 109
  36. 365
  37. 181
  38. 338
  39. 298
  40. 47

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