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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 937 · 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. 1.230 + 348 =
  2. 2.559 + 484 =
  3. 3.260 + 396 =
  4. 4.193 + 249 =
  5. 5.957 − 407 =
  6. 6.427 − 226 =
  7. 7.366 + 478 =
  8. 8.904 − 389 =
  9. 9.666 + 482 =
  10. 10.454 − 351 =
  11. 11.572 + 158 =
  12. 12.303 + 169 =
  13. 13.173 + 224 =
  14. 14.218 + 491 =
  15. 15.348 + 314 =
  16. 16.244 + 563 =
  17. 17.547 + 379 =
  18. 18.417 + 496 =
  19. 19.581 − 474 =
  20. 20.544 − 413 =
  21. 21.869 − 201 =
  22. 22.639 − 129 =
  23. 23.578 − 291 =
  24. 24.470 − 151 =
  25. 25.579 + 301 =
  26. 26.718 − 204 =
  27. 27.491 + 511 =
  28. 28.229 + 429 =
  29. 29.682 − 132 =
  30. 30.307 + 476 =
  31. 31.751 − 218 =
  32. 32.636 + 338 =
  33. 33.583 + 282 =
  34. 34.573 − 473 =
  35. 35.925 − 279 =
  36. 36.621 + 617 =
  37. 37.680 + 365 =
  38. 38.731 − 451 =
  39. 39.561 + 555 =
  40. 40.306 + 626 =

Answer key

  1. 578
  2. 1043
  3. 656
  4. 442
  5. 550
  6. 201
  7. 844
  8. 515
  9. 1148
  10. 103
  11. 730
  12. 472
  13. 397
  14. 709
  15. 662
  16. 807
  17. 926
  18. 913
  19. 107
  20. 131
  21. 668
  22. 510
  23. 287
  24. 319
  25. 880
  26. 514
  27. 1002
  28. 658
  29. 550
  30. 783
  31. 533
  32. 974
  33. 865
  34. 100
  35. 646
  36. 1238
  37. 1045
  38. 280
  39. 1116
  40. 932

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