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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 413 · 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. 1.909 − 599 =
  2. 2.832 − 799 =
  3. 3.658 − 299 =
  4. 4.817 − 539 =
  5. 5.887 − 487 =
  6. 6.469 − 149 =
  7. 7.439 − 399 =
  8. 8.861 − 199 =
  9. 9.461 − 299 =
  10. 10.782 − 318 =
  11. 11.501 − 337 =
  12. 12.484 − 399 =
  13. 13.365 − 347 =
  14. 14.461 − 198 =
  15. 15.763 − 597 =
  16. 16.781 − 277 =
  17. 17.544 − 157 =
  18. 18.559 − 188 =
  19. 19.947 − 587 =
  20. 20.882 − 799 =
  21. 21.842 − 399 =
  22. 22.828 − 297 =
  23. 23.722 − 419 =
  24. 24.709 − 169 =
  25. 25.988 − 697 =
  26. 26.802 − 697 =
  27. 27.544 − 497 =
  28. 28.327 − 197 =
  29. 29.744 − 297 =
  30. 30.935 − 199 =
  31. 31.884 − 798 =
  32. 32.825 − 599 =
  33. 33.388 − 237 =
  34. 34.410 − 199 =
  35. 35.539 − 199 =
  36. 36.579 − 498 =
  37. 37.498 − 218 =
  38. 38.317 − 299 =
  39. 39.768 − 697 =
  40. 40.716 − 159 =

Answer key

  1. 310
  2. 33
  3. 359
  4. 278
  5. 400
  6. 320
  7. 40
  8. 662
  9. 162
  10. 464
  11. 164
  12. 85
  13. 18
  14. 263
  15. 166
  16. 504
  17. 387
  18. 371
  19. 360
  20. 83
  21. 443
  22. 531
  23. 303
  24. 540
  25. 291
  26. 105
  27. 47
  28. 130
  29. 447
  30. 736
  31. 86
  32. 226
  33. 151
  34. 211
  35. 340
  36. 81
  37. 280
  38. 18
  39. 71
  40. 557

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