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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 4 · 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. 1.857 − 649 =
  2. 2.370 − 259 =
  3. 3.665 − 307 =
  4. 4.821 − 267 =
  5. 5.657 − 607 =
  6. 6.955 − 678 =
  7. 7.617 − 497 =
  8. 8.701 − 669 =
  9. 9.732 − 297 =
  10. 10.958 − 677 =
  11. 11.581 − 178 =
  12. 12.830 − 597 =
  13. 13.917 − 298 =
  14. 14.603 − 459 =
  15. 15.674 − 657 =
  16. 16.902 − 668 =
  17. 17.413 − 397 =
  18. 18.889 − 627 =
  19. 19.465 − 339 =
  20. 20.423 − 247 =
  21. 21.682 − 437 =
  22. 22.853 − 599 =
  23. 23.574 − 199 =
  24. 24.935 − 318 =
  25. 25.718 − 518 =
  26. 26.810 − 297 =
  27. 27.677 − 199 =
  28. 28.663 − 647 =
  29. 29.555 − 478 =
  30. 30.669 − 618 =
  31. 31.750 − 669 =
  32. 32.504 − 467 =
  33. 33.610 − 548 =
  34. 34.951 − 518 =
  35. 35.542 − 257 =
  36. 36.845 − 599 =
  37. 37.835 − 689 =
  38. 38.801 − 329 =
  39. 39.697 − 297 =
  40. 40.588 − 228 =

Answer key

  1. 208
  2. 111
  3. 358
  4. 554
  5. 50
  6. 277
  7. 120
  8. 32
  9. 435
  10. 281
  11. 403
  12. 233
  13. 619
  14. 144
  15. 17
  16. 234
  17. 16
  18. 262
  19. 126
  20. 176
  21. 245
  22. 254
  23. 375
  24. 617
  25. 200
  26. 513
  27. 478
  28. 16
  29. 77
  30. 51
  31. 81
  32. 37
  33. 62
  34. 433
  35. 285
  36. 246
  37. 146
  38. 472
  39. 400
  40. 360

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