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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 400 · 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. 1.583 + 227 =
  2. 2.628 + 135 =
  3. 3.408 + 125 =
  4. 4.651 + 154 =
  5. 5.473 − 157 =
  6. 6.703 − 144 =
  7. 7.189 + 517 =
  8. 8.260 + 447 =
  9. 9.650 + 567 =
  10. 10.611 + 214 =
  11. 11.524 − 297 =
  12. 12.749 + 536 =
  13. 13.162 + 449 =
  14. 14.447 − 288 =
  15. 15.581 − 419 =
  16. 16.235 + 383 =
  17. 17.436 − 168 =
  18. 18.648 − 214 =
  19. 19.467 + 641 =
  20. 20.784 − 258 =
  21. 21.969 − 503 =
  22. 22.759 + 115 =
  23. 23.581 + 197 =
  24. 24.615 − 352 =
  25. 25.597 − 319 =
  26. 26.579 + 503 =
  27. 27.586 + 266 =
  28. 28.687 − 272 =
  29. 29.668 + 669 =
  30. 30.987 − 332 =
  31. 31.646 + 461 =
  32. 32.471 + 265 =
  33. 33.598 + 217 =
  34. 34.708 + 628 =
  35. 35.135 + 156 =
  36. 36.643 − 505 =
  37. 37.727 + 499 =
  38. 38.264 + 368 =
  39. 39.708 + 444 =
  40. 40.466 − 326 =

Answer key

  1. 810
  2. 763
  3. 533
  4. 805
  5. 316
  6. 559
  7. 706
  8. 707
  9. 1217
  10. 825
  11. 227
  12. 1285
  13. 611
  14. 159
  15. 162
  16. 618
  17. 268
  18. 434
  19. 1108
  20. 526
  21. 466
  22. 874
  23. 778
  24. 263
  25. 278
  26. 1082
  27. 852
  28. 415
  29. 1337
  30. 655
  31. 1107
  32. 736
  33. 815
  34. 1336
  35. 291
  36. 138
  37. 1226
  38. 632
  39. 1152
  40. 140

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