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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 731 · 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. 1.267 + 251 =
  2. 2.458 + 147 =
  3. 3.532 + 326 =
  4. 4.748 + 297 =
  5. 5.668 + 517 =
  6. 6.456 − 235 =
  7. 7.945 − 677 =
  8. 8.639 + 245 =
  9. 9.526 − 416 =
  10. 10.430 − 196 =
  11. 11.325 + 313 =
  12. 12.859 − 316 =
  13. 13.378 + 261 =
  14. 14.597 − 321 =
  15. 15.716 + 275 =
  16. 16.310 + 324 =
  17. 17.571 − 235 =
  18. 18.303 + 273 =
  19. 19.758 − 643 =
  20. 20.265 + 556 =
  21. 21.655 + 189 =
  22. 22.931 − 322 =
  23. 23.458 + 494 =
  24. 24.600 − 376 =
  25. 25.326 + 395 =
  26. 26.587 − 219 =
  27. 27.563 + 201 =
  28. 28.353 + 626 =
  29. 29.249 + 211 =
  30. 30.639 − 493 =
  31. 31.558 − 181 =
  32. 32.232 + 236 =
  33. 33.653 + 415 =
  34. 34.623 − 142 =
  35. 35.879 − 363 =
  36. 36.880 − 256 =
  37. 37.144 + 377 =
  38. 38.772 + 526 =
  39. 39.156 + 467 =
  40. 40.757 − 474 =

Answer key

  1. 518
  2. 605
  3. 858
  4. 1045
  5. 1185
  6. 221
  7. 268
  8. 884
  9. 110
  10. 234
  11. 638
  12. 543
  13. 639
  14. 276
  15. 991
  16. 634
  17. 336
  18. 576
  19. 115
  20. 821
  21. 844
  22. 609
  23. 952
  24. 224
  25. 721
  26. 368
  27. 764
  28. 979
  29. 460
  30. 146
  31. 377
  32. 468
  33. 1068
  34. 481
  35. 516
  36. 624
  37. 521
  38. 1298
  39. 623
  40. 283

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