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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 126 · 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. 1.707 − 313 =
  2. 2.456 − 121 =
  3. 3.271 + 676 =
  4. 4.506 + 161 =
  5. 5.505 − 388 =
  6. 6.169 + 536 =
  7. 7.588 + 478 =
  8. 8.501 − 318 =
  9. 9.134 + 179 =
  10. 10.662 + 321 =
  11. 11.488 + 195 =
  12. 12.700 − 517 =
  13. 13.641 + 556 =
  14. 14.566 + 321 =
  15. 15.193 + 213 =
  16. 16.318 + 195 =
  17. 17.726 + 229 =
  18. 18.221 + 396 =
  19. 19.816 − 378 =
  20. 20.327 + 519 =
  21. 21.451 − 136 =
  22. 22.440 − 202 =
  23. 23.481 − 256 =
  24. 24.643 + 371 =
  25. 25.462 + 473 =
  26. 26.858 − 234 =
  27. 27.352 + 392 =
  28. 28.483 − 245 =
  29. 29.477 + 279 =
  30. 30.976 − 416 =
  31. 31.564 − 239 =
  32. 32.360 + 671 =
  33. 33.484 + 547 =
  34. 34.284 + 674 =
  35. 35.815 − 549 =
  36. 36.731 − 473 =
  37. 37.592 − 448 =
  38. 38.989 − 145 =
  39. 39.295 + 342 =
  40. 40.807 − 513 =

Answer key

  1. 394
  2. 335
  3. 947
  4. 667
  5. 117
  6. 705
  7. 1066
  8. 183
  9. 313
  10. 983
  11. 683
  12. 183
  13. 1197
  14. 887
  15. 406
  16. 513
  17. 955
  18. 617
  19. 438
  20. 846
  21. 315
  22. 238
  23. 225
  24. 1014
  25. 935
  26. 624
  27. 744
  28. 238
  29. 756
  30. 560
  31. 325
  32. 1031
  33. 1031
  34. 958
  35. 266
  36. 258
  37. 144
  38. 844
  39. 637
  40. 294

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