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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 699 · 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. 1.288 + 685 =
  2. 2.886 − 486 =
  3. 3.413 + 428 =
  4. 4.553 + 141 =
  5. 5.567 + 116 =
  6. 6.657 + 251 =
  7. 7.195 + 138 =
  8. 8.259 + 582 =
  9. 9.208 + 571 =
  10. 10.309 + 306 =
  11. 11.447 − 164 =
  12. 12.415 + 353 =
  13. 13.643 + 688 =
  14. 14.508 − 262 =
  15. 15.157 + 375 =
  16. 16.186 + 644 =
  17. 17.839 − 161 =
  18. 18.749 − 485 =
  19. 19.688 + 662 =
  20. 20.664 − 153 =
  21. 21.699 − 318 =
  22. 22.747 + 225 =
  23. 23.769 − 177 =
  24. 24.319 + 192 =
  25. 25.643 + 238 =
  26. 26.482 + 352 =
  27. 27.761 − 638 =
  28. 28.941 − 823 =
  29. 29.696 + 133 =
  30. 30.738 + 611 =
  31. 31.738 + 643 =
  32. 32.505 − 395 =
  33. 33.645 − 116 =
  34. 34.577 − 309 =
  35. 35.806 − 555 =
  36. 36.934 − 361 =
  37. 37.208 + 564 =
  38. 38.655 − 394 =
  39. 39.525 + 267 =
  40. 40.537 − 186 =

Answer key

  1. 973
  2. 400
  3. 841
  4. 694
  5. 683
  6. 908
  7. 333
  8. 841
  9. 779
  10. 615
  11. 283
  12. 768
  13. 1331
  14. 246
  15. 532
  16. 830
  17. 678
  18. 264
  19. 1350
  20. 511
  21. 381
  22. 972
  23. 592
  24. 511
  25. 881
  26. 834
  27. 123
  28. 118
  29. 829
  30. 1349
  31. 1381
  32. 110
  33. 529
  34. 268
  35. 251
  36. 573
  37. 772
  38. 261
  39. 792
  40. 351

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