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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 547 · 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. 1.356 − 199 =
  2. 2.568 − 499 =
  3. 3.761 − 619 =
  4. 4.377 − 298 =
  5. 5.759 − 209 =
  6. 6.804 − 299 =
  7. 7.855 − 799 =
  8. 8.917 − 798 =
  9. 9.764 − 129 =
  10. 10.415 − 399 =
  11. 11.726 − 498 =
  12. 12.780 − 169 =
  13. 13.868 − 299 =
  14. 14.707 − 389 =
  15. 15.963 − 579 =
  16. 16.389 − 299 =
  17. 17.551 − 408 =
  18. 18.886 − 199 =
  19. 19.355 − 317 =
  20. 20.999 − 397 =
  21. 21.979 − 389 =
  22. 22.617 − 489 =
  23. 23.839 − 497 =
  24. 24.214 − 198 =
  25. 25.236 − 197 =
  26. 26.305 − 147 =
  27. 27.818 − 299 =
  28. 28.441 − 297 =
  29. 29.726 − 589 =
  30. 30.821 − 799 =
  31. 31.800 − 398 =
  32. 32.505 − 399 =
  33. 33.943 − 397 =
  34. 34.589 − 299 =
  35. 35.731 − 598 =
  36. 36.825 − 798 =
  37. 37.761 − 678 =
  38. 38.365 − 158 =
  39. 39.548 − 398 =
  40. 40.875 − 468 =

Answer key

  1. 157
  2. 69
  3. 142
  4. 79
  5. 550
  6. 505
  7. 56
  8. 119
  9. 635
  10. 16
  11. 228
  12. 611
  13. 569
  14. 318
  15. 384
  16. 90
  17. 143
  18. 687
  19. 38
  20. 602
  21. 590
  22. 128
  23. 342
  24. 16
  25. 39
  26. 158
  27. 519
  28. 144
  29. 137
  30. 22
  31. 402
  32. 106
  33. 546
  34. 290
  35. 133
  36. 27
  37. 83
  38. 207
  39. 150
  40. 407

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