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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 488 · 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. 1.648 + 187 =
  2. 2.552 + 571 =
  3. 3.441 − 132 =
  4. 4.971 − 512 =
  5. 5.471 + 687 =
  6. 6.530 + 605 =
  7. 7.506 − 193 =
  8. 8.503 − 222 =
  9. 9.862 − 173 =
  10. 10.355 + 617 =
  11. 11.536 + 309 =
  12. 12.304 + 113 =
  13. 13.456 + 653 =
  14. 14.470 + 685 =
  15. 15.362 + 383 =
  16. 16.304 + 238 =
  17. 17.470 + 211 =
  18. 18.191 + 231 =
  19. 19.841 − 275 =
  20. 20.769 + 291 =
  21. 21.296 + 587 =
  22. 22.593 − 121 =
  23. 23.984 − 136 =
  24. 24.662 + 153 =
  25. 25.644 + 274 =
  26. 26.157 + 482 =
  27. 27.448 + 576 =
  28. 28.522 − 383 =
  29. 29.359 + 357 =
  30. 30.152 + 542 =
  31. 31.630 − 489 =
  32. 32.524 + 365 =
  33. 33.299 + 195 =
  34. 34.659 + 142 =
  35. 35.224 + 678 =
  36. 36.266 + 334 =
  37. 37.412 − 191 =
  38. 38.628 + 381 =
  39. 39.404 + 371 =
  40. 40.554 − 445 =

Answer key

  1. 835
  2. 1123
  3. 309
  4. 459
  5. 1158
  6. 1135
  7. 313
  8. 281
  9. 689
  10. 972
  11. 845
  12. 417
  13. 1109
  14. 1155
  15. 745
  16. 542
  17. 681
  18. 422
  19. 566
  20. 1060
  21. 883
  22. 472
  23. 848
  24. 815
  25. 918
  26. 639
  27. 1024
  28. 139
  29. 716
  30. 694
  31. 141
  32. 889
  33. 494
  34. 801
  35. 902
  36. 600
  37. 221
  38. 1009
  39. 775
  40. 109

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