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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 54 · 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. 1.199 + 128 =
  2. 2.504 + 621 =
  3. 3.852 − 367 =
  4. 4.655 − 296 =
  5. 5.581 + 133 =
  6. 6.649 − 491 =
  7. 7.776 − 633 =
  8. 8.300 + 288 =
  9. 9.670 − 375 =
  10. 10.574 − 197 =
  11. 11.150 + 222 =
  12. 12.700 + 211 =
  13. 13.389 + 174 =
  14. 14.378 + 206 =
  15. 15.788 − 201 =
  16. 16.296 + 298 =
  17. 17.756 − 305 =
  18. 18.577 + 354 =
  19. 19.236 + 356 =
  20. 20.682 − 121 =
  21. 21.342 + 476 =
  22. 22.389 + 461 =
  23. 23.207 + 167 =
  24. 24.325 + 589 =
  25. 25.805 − 412 =
  26. 26.431 − 235 =
  27. 27.777 + 583 =
  28. 28.501 − 384 =
  29. 29.477 + 217 =
  30. 30.896 − 617 =
  31. 31.683 − 331 =
  32. 32.436 − 306 =
  33. 33.193 + 483 =
  34. 34.780 − 277 =
  35. 35.787 + 349 =
  36. 36.976 − 554 =
  37. 37.564 − 251 =
  38. 38.230 + 671 =
  39. 39.916 − 311 =
  40. 40.564 − 234 =

Answer key

  1. 327
  2. 1125
  3. 485
  4. 359
  5. 714
  6. 158
  7. 143
  8. 588
  9. 295
  10. 377
  11. 372
  12. 911
  13. 563
  14. 584
  15. 587
  16. 594
  17. 451
  18. 931
  19. 592
  20. 561
  21. 818
  22. 850
  23. 374
  24. 914
  25. 393
  26. 196
  27. 1360
  28. 117
  29. 694
  30. 279
  31. 352
  32. 130
  33. 676
  34. 503
  35. 1136
  36. 422
  37. 313
  38. 901
  39. 605
  40. 330

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