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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 905 · 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. 1.348 + 278 =
  2. 2.780 − 258 =
  3. 3.485 − 333 =
  4. 4.824 − 481 =
  5. 5.660 − 289 =
  6. 6.556 + 542 =
  7. 7.803 − 211 =
  8. 8.759 − 577 =
  9. 9.492 − 339 =
  10. 10.659 + 154 =
  11. 11.188 + 636 =
  12. 12.921 − 689 =
  13. 13.440 − 225 =
  14. 14.739 + 163 =
  15. 15.425 − 229 =
  16. 16.680 − 529 =
  17. 17.643 + 459 =
  18. 18.390 + 159 =
  19. 19.681 − 246 =
  20. 20.496 − 141 =
  21. 21.565 − 206 =
  22. 22.714 + 576 =
  23. 23.844 − 326 =
  24. 24.928 − 417 =
  25. 25.481 + 201 =
  26. 26.701 + 456 =
  27. 27.461 + 399 =
  28. 28.607 − 196 =
  29. 29.200 + 291 =
  30. 30.770 − 651 =
  31. 31.191 + 113 =
  32. 32.970 − 685 =
  33. 33.973 − 573 =
  34. 34.292 + 291 =
  35. 35.790 − 291 =
  36. 36.411 + 395 =
  37. 37.168 + 673 =
  38. 38.765 − 213 =
  39. 39.574 − 455 =
  40. 40.607 − 359 =

Answer key

  1. 626
  2. 522
  3. 152
  4. 343
  5. 371
  6. 1098
  7. 592
  8. 182
  9. 153
  10. 813
  11. 824
  12. 232
  13. 215
  14. 902
  15. 196
  16. 151
  17. 1102
  18. 549
  19. 435
  20. 355
  21. 359
  22. 1290
  23. 518
  24. 511
  25. 682
  26. 1157
  27. 860
  28. 411
  29. 491
  30. 119
  31. 304
  32. 285
  33. 400
  34. 583
  35. 499
  36. 806
  37. 841
  38. 552
  39. 119
  40. 248

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