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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 99 · 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. 1.795 − 675 =
  2. 2.654 + 378 =
  3. 3.752 + 562 =
  4. 4.695 − 477 =
  5. 5.729 − 332 =
  6. 6.268 + 641 =
  7. 7.615 + 551 =
  8. 8.757 + 315 =
  9. 9.240 + 381 =
  10. 10.777 − 416 =
  11. 11.401 + 171 =
  12. 12.427 − 296 =
  13. 13.485 − 331 =
  14. 14.264 + 245 =
  15. 15.292 + 146 =
  16. 16.473 − 239 =
  17. 17.291 + 424 =
  18. 18.657 + 119 =
  19. 19.392 + 463 =
  20. 20.517 − 119 =
  21. 21.694 − 133 =
  22. 22.767 + 248 =
  23. 23.687 + 687 =
  24. 24.517 + 343 =
  25. 25.432 − 221 =
  26. 26.484 − 153 =
  27. 27.252 + 254 =
  28. 28.367 + 445 =
  29. 29.653 − 544 =
  30. 30.590 + 474 =
  31. 31.741 + 489 =
  32. 32.249 + 519 =
  33. 33.847 − 677 =
  34. 34.447 − 158 =
  35. 35.137 + 168 =
  36. 36.569 + 269 =
  37. 37.649 − 388 =
  38. 38.184 + 314 =
  39. 39.617 + 268 =
  40. 40.663 + 275 =

Answer key

  1. 120
  2. 1032
  3. 1314
  4. 218
  5. 397
  6. 909
  7. 1166
  8. 1072
  9. 621
  10. 361
  11. 572
  12. 131
  13. 154
  14. 509
  15. 438
  16. 234
  17. 715
  18. 776
  19. 855
  20. 398
  21. 561
  22. 1015
  23. 1374
  24. 860
  25. 211
  26. 331
  27. 506
  28. 812
  29. 109
  30. 1064
  31. 1230
  32. 768
  33. 170
  34. 289
  35. 305
  36. 838
  37. 261
  38. 498
  39. 885
  40. 938

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