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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 297 · 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. 1.911 − 199 =
  2. 2.842 − 529 =
  3. 3.895 − 599 =
  4. 4.810 − 598 =
  5. 5.362 − 268 =
  6. 6.996 − 698 =
  7. 7.878 − 669 =
  8. 8.479 − 287 =
  9. 9.975 − 799 =
  10. 10.936 − 798 =
  11. 11.781 − 497 =
  12. 12.415 − 228 =
  13. 13.394 − 299 =
  14. 14.690 − 607 =
  15. 15.376 − 297 =
  16. 16.620 − 499 =
  17. 17.950 − 177 =
  18. 18.447 − 198 =
  19. 19.567 − 399 =
  20. 20.847 − 508 =
  21. 21.797 − 399 =
  22. 22.681 − 598 =
  23. 23.787 − 397 =
  24. 24.852 − 197 =
  25. 25.706 − 299 =
  26. 26.771 − 388 =
  27. 27.422 − 399 =
  28. 28.755 − 497 =
  29. 29.912 − 798 =
  30. 30.750 − 689 =
  31. 31.691 − 299 =
  32. 32.839 − 399 =
  33. 33.973 − 698 =
  34. 34.889 − 518 =
  35. 35.621 − 557 =
  36. 36.769 − 599 =
  37. 37.616 − 597 =
  38. 38.712 − 599 =
  39. 39.335 − 277 =
  40. 40.908 − 428 =

Answer key

  1. 712
  2. 313
  3. 296
  4. 212
  5. 94
  6. 298
  7. 209
  8. 192
  9. 176
  10. 138
  11. 284
  12. 187
  13. 95
  14. 83
  15. 79
  16. 121
  17. 773
  18. 249
  19. 168
  20. 339
  21. 398
  22. 83
  23. 390
  24. 655
  25. 407
  26. 383
  27. 23
  28. 258
  29. 114
  30. 61
  31. 392
  32. 440
  33. 275
  34. 371
  35. 64
  36. 170
  37. 19
  38. 113
  39. 58
  40. 480

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