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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 245 · 40 questions
TalentJR

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

NameDateTime takenScore ___ / 40
  1. 1.192 + 164 =
  2. 2.657 + 492 =
  3. 3.647 − 287 =
  4. 4.405 + 507 =
  5. 5.695 + 433 =
  6. 6.555 + 454 =
  7. 7.559 − 141 =
  8. 8.564 + 607 =
  9. 9.772 + 651 =
  10. 10.632 + 434 =
  11. 11.899 − 508 =
  12. 12.750 − 199 =
  13. 13.654 − 474 =
  14. 14.497 − 381 =
  15. 15.715 − 516 =
  16. 16.618 + 408 =
  17. 17.663 − 336 =
  18. 18.924 − 361 =
  19. 19.300 + 641 =
  20. 20.131 + 235 =
  21. 21.479 − 301 =
  22. 22.565 − 332 =
  23. 23.768 + 113 =
  24. 24.632 + 385 =
  25. 25.215 + 437 =
  26. 26.640 − 292 =
  27. 27.504 − 361 =
  28. 28.813 − 226 =
  29. 29.336 + 121 =
  30. 30.642 + 287 =
  31. 31.708 − 151 =
  32. 32.327 + 652 =
  33. 33.470 − 181 =
  34. 34.758 − 459 =
  35. 35.438 + 153 =
  36. 36.670 + 552 =
  37. 37.247 + 429 =
  38. 38.597 − 368 =
  39. 39.767 + 169 =
  40. 40.190 + 547 =

Answer key

  1. 356
  2. 1149
  3. 360
  4. 912
  5. 1128
  6. 1009
  7. 418
  8. 1171
  9. 1423
  10. 1066
  11. 391
  12. 551
  13. 180
  14. 116
  15. 199
  16. 1026
  17. 327
  18. 563
  19. 941
  20. 366
  21. 178
  22. 233
  23. 881
  24. 1017
  25. 652
  26. 348
  27. 143
  28. 587
  29. 457
  30. 929
  31. 557
  32. 979
  33. 289
  34. 299
  35. 591
  36. 1222
  37. 676
  38. 229
  39. 936
  40. 737

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