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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 217 · 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. 1.557 − 418 =
  2. 2.503 − 226 =
  3. 3.807 − 599 =
  4. 4.311 + 196 =
  5. 5.351 + 562 =
  6. 6.953 − 351 =
  7. 7.627 − 263 =
  8. 8.642 + 222 =
  9. 9.975 − 605 =
  10. 10.908 − 557 =
  11. 11.304 + 243 =
  12. 12.733 + 215 =
  13. 13.271 + 625 =
  14. 14.541 − 375 =
  15. 15.945 − 838 =
  16. 16.436 − 271 =
  17. 17.977 − 756 =
  18. 18.459 − 273 =
  19. 19.643 − 463 =
  20. 20.203 + 585 =
  21. 21.601 + 332 =
  22. 22.172 + 387 =
  23. 23.266 + 588 =
  24. 24.524 + 476 =
  25. 25.749 + 173 =
  26. 26.820 − 343 =
  27. 27.747 + 395 =
  28. 28.487 − 271 =
  29. 29.360 + 293 =
  30. 30.440 + 681 =
  31. 31.366 + 391 =
  32. 32.487 − 272 =
  33. 33.728 − 455 =
  34. 34.290 + 123 =
  35. 35.460 − 261 =
  36. 36.567 − 246 =
  37. 37.945 − 461 =
  38. 38.145 + 351 =
  39. 39.533 − 158 =
  40. 40.519 + 496 =

Answer key

  1. 139
  2. 277
  3. 208
  4. 507
  5. 913
  6. 602
  7. 364
  8. 864
  9. 370
  10. 351
  11. 547
  12. 948
  13. 896
  14. 166
  15. 107
  16. 165
  17. 221
  18. 186
  19. 180
  20. 788
  21. 933
  22. 559
  23. 854
  24. 1000
  25. 922
  26. 477
  27. 1142
  28. 216
  29. 653
  30. 1121
  31. 757
  32. 215
  33. 273
  34. 413
  35. 199
  36. 321
  37. 484
  38. 496
  39. 375
  40. 1015

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