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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 128 · 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. 1.809 − 621 =
  2. 2.430 + 601 =
  3. 3.481 − 134 =
  4. 4.240 + 406 =
  5. 5.471 − 273 =
  6. 6.139 + 112 =
  7. 7.649 + 428 =
  8. 8.979 − 219 =
  9. 9.816 − 226 =
  10. 10.487 + 499 =
  11. 11.259 + 163 =
  12. 12.802 − 277 =
  13. 13.638 − 465 =
  14. 14.316 + 221 =
  15. 15.209 + 245 =
  16. 16.432 + 403 =
  17. 17.525 − 398 =
  18. 18.560 − 271 =
  19. 19.425 − 123 =
  20. 20.562 − 113 =
  21. 21.760 − 154 =
  22. 22.130 + 361 =
  23. 23.676 + 195 =
  24. 24.584 − 229 =
  25. 25.460 − 246 =
  26. 26.446 + 633 =
  27. 27.241 + 274 =
  28. 28.493 − 271 =
  29. 29.823 − 334 =
  30. 30.716 − 575 =
  31. 31.754 − 449 =
  32. 32.718 − 547 =
  33. 33.551 + 233 =
  34. 34.398 + 403 =
  35. 35.287 + 394 =
  36. 36.183 + 301 =
  37. 37.586 − 199 =
  38. 38.542 + 602 =
  39. 39.867 − 115 =
  40. 40.694 + 273 =

Answer key

  1. 188
  2. 1031
  3. 347
  4. 646
  5. 198
  6. 251
  7. 1077
  8. 760
  9. 590
  10. 986
  11. 422
  12. 525
  13. 173
  14. 537
  15. 454
  16. 835
  17. 127
  18. 289
  19. 302
  20. 449
  21. 606
  22. 491
  23. 871
  24. 355
  25. 214
  26. 1079
  27. 515
  28. 222
  29. 489
  30. 141
  31. 305
  32. 171
  33. 784
  34. 801
  35. 681
  36. 484
  37. 387
  38. 1144
  39. 752
  40. 967

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