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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 681 · 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. 1.362 − 318 =
  2. 2.257 − 197 =
  3. 3.924 − 137 =
  4. 4.924 − 299 =
  5. 5.693 − 629 =
  6. 6.714 − 697 =
  7. 7.840 − 698 =
  8. 8.890 − 158 =
  9. 9.681 − 399 =
  10. 10.729 − 697 =
  11. 11.587 − 149 =
  12. 12.466 − 399 =
  13. 13.781 − 398 =
  14. 14.716 − 699 =
  15. 15.481 − 397 =
  16. 16.554 − 399 =
  17. 17.901 − 168 =
  18. 18.645 − 599 =
  19. 19.964 − 619 =
  20. 20.649 − 559 =
  21. 21.872 − 799 =
  22. 22.847 − 798 =
  23. 23.634 − 609 =
  24. 24.259 − 119 =
  25. 25.980 − 448 =
  26. 26.519 − 299 =
  27. 27.744 − 688 =
  28. 28.927 − 798 =
  29. 29.346 − 318 =
  30. 30.238 − 129 =
  31. 31.883 − 299 =
  32. 32.708 − 649 =
  33. 33.992 − 219 =
  34. 34.778 − 699 =
  35. 35.839 − 619 =
  36. 36.241 − 199 =
  37. 37.975 − 799 =
  38. 38.729 − 599 =
  39. 39.976 − 318 =
  40. 40.447 − 128 =

Answer key

  1. 44
  2. 60
  3. 787
  4. 625
  5. 64
  6. 17
  7. 142
  8. 732
  9. 282
  10. 32
  11. 438
  12. 67
  13. 383
  14. 17
  15. 84
  16. 155
  17. 733
  18. 46
  19. 345
  20. 90
  21. 73
  22. 49
  23. 25
  24. 140
  25. 532
  26. 220
  27. 56
  28. 129
  29. 28
  30. 109
  31. 584
  32. 59
  33. 773
  34. 79
  35. 220
  36. 42
  37. 176
  38. 130
  39. 658
  40. 319

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