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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 484 · 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. 1.550 − 297 =
  2. 2.705 + 461 =
  3. 3.224 + 611 =
  4. 4.735 − 445 =
  5. 5.723 + 351 =
  6. 6.976 − 721 =
  7. 7.688 + 251 =
  8. 8.912 − 802 =
  9. 9.905 − 576 =
  10. 10.433 + 665 =
  11. 11.669 + 601 =
  12. 12.221 + 335 =
  13. 13.773 − 657 =
  14. 14.422 − 146 =
  15. 15.487 + 572 =
  16. 16.681 + 329 =
  17. 17.229 + 582 =
  18. 18.542 + 142 =
  19. 19.708 + 273 =
  20. 20.627 + 188 =
  21. 21.957 − 146 =
  22. 22.484 + 519 =
  23. 23.594 − 319 =
  24. 24.383 + 181 =
  25. 25.572 − 311 =
  26. 26.358 + 433 =
  27. 27.687 + 454 =
  28. 28.747 + 172 =
  29. 29.160 + 174 =
  30. 30.194 + 637 =
  31. 31.640 + 602 =
  32. 32.232 + 164 =
  33. 33.232 + 591 =
  34. 34.201 + 164 =
  35. 35.525 − 359 =
  36. 36.476 − 345 =
  37. 37.423 + 136 =
  38. 38.903 − 411 =
  39. 39.905 − 378 =
  40. 40.357 + 166 =

Answer key

  1. 253
  2. 1166
  3. 835
  4. 290
  5. 1074
  6. 255
  7. 939
  8. 110
  9. 329
  10. 1098
  11. 1270
  12. 556
  13. 116
  14. 276
  15. 1059
  16. 1010
  17. 811
  18. 684
  19. 981
  20. 815
  21. 811
  22. 1003
  23. 275
  24. 564
  25. 261
  26. 791
  27. 1141
  28. 919
  29. 334
  30. 831
  31. 1242
  32. 396
  33. 823
  34. 365
  35. 166
  36. 131
  37. 559
  38. 492
  39. 527
  40. 523

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