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Subtraction by Rounding Worksheet

Mental maths lesson 21: Subtract by rounding up and adding back · Set 949 · 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. 1.561 − 157 =
  2. 2.367 − 298 =
  3. 3.898 − 598 =
  4. 4.575 − 549 =
  5. 5.523 − 469 =
  6. 6.994 − 189 =
  7. 7.795 − 497 =
  8. 8.635 − 607 =
  9. 9.832 − 599 =
  10. 10.575 − 288 =
  11. 11.934 − 297 =
  12. 12.822 − 598 =
  13. 13.881 − 498 =
  14. 14.906 − 398 =
  15. 15.621 − 198 =
  16. 16.629 − 597 =
  17. 17.933 − 598 =
  18. 18.847 − 698 =
  19. 19.239 − 119 =
  20. 20.470 − 349 =
  21. 21.725 − 298 =
  22. 22.788 − 607 =
  23. 23.705 − 198 =
  24. 24.795 − 558 =
  25. 25.745 − 407 =
  26. 26.793 − 609 =
  27. 27.358 − 269 =
  28. 28.573 − 289 =
  29. 29.968 − 677 =
  30. 30.808 − 499 =
  31. 31.655 − 497 =
  32. 32.840 − 799 =
  33. 33.584 − 399 =
  34. 34.626 − 539 =
  35. 35.863 − 297 =
  36. 36.925 − 428 =
  37. 37.284 − 197 =
  38. 38.737 − 297 =
  39. 39.540 − 397 =
  40. 40.668 − 479 =

Answer key

  1. 404
  2. 69
  3. 300
  4. 26
  5. 54
  6. 805
  7. 298
  8. 28
  9. 233
  10. 287
  11. 637
  12. 224
  13. 383
  14. 508
  15. 423
  16. 32
  17. 335
  18. 149
  19. 120
  20. 121
  21. 427
  22. 181
  23. 507
  24. 237
  25. 338
  26. 184
  27. 89
  28. 284
  29. 291
  30. 309
  31. 158
  32. 41
  33. 185
  34. 87
  35. 566
  36. 497
  37. 87
  38. 440
  39. 143
  40. 189

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