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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 553 · 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. 1.645 + 333 =
  2. 2.842 − 131 =
  3. 3.335 + 458 =
  4. 4.903 − 144 =
  5. 5.265 + 136 =
  6. 6.679 − 182 =
  7. 7.259 + 328 =
  8. 8.860 − 367 =
  9. 9.742 + 134 =
  10. 10.653 + 559 =
  11. 11.191 + 244 =
  12. 12.800 − 532 =
  13. 13.678 − 187 =
  14. 14.295 + 149 =
  15. 15.504 − 312 =
  16. 16.517 + 454 =
  17. 17.335 + 682 =
  18. 18.736 − 478 =
  19. 19.694 − 243 =
  20. 20.553 − 356 =
  21. 21.731 − 313 =
  22. 22.771 − 124 =
  23. 23.899 − 692 =
  24. 24.469 − 133 =
  25. 25.150 + 336 =
  26. 26.737 + 652 =
  27. 27.321 + 658 =
  28. 28.514 − 328 =
  29. 29.499 − 275 =
  30. 30.363 + 291 =
  31. 31.640 − 251 =
  32. 32.849 − 156 =
  33. 33.216 + 515 =
  34. 34.611 + 299 =
  35. 35.514 + 337 =
  36. 36.408 + 282 =
  37. 37.181 + 532 =
  38. 38.353 + 231 =
  39. 39.733 − 359 =
  40. 40.599 + 636 =

Answer key

  1. 978
  2. 711
  3. 793
  4. 759
  5. 401
  6. 497
  7. 587
  8. 493
  9. 876
  10. 1212
  11. 435
  12. 268
  13. 491
  14. 444
  15. 192
  16. 971
  17. 1017
  18. 258
  19. 451
  20. 197
  21. 418
  22. 647
  23. 207
  24. 336
  25. 486
  26. 1389
  27. 979
  28. 186
  29. 224
  30. 654
  31. 389
  32. 693
  33. 731
  34. 910
  35. 851
  36. 690
  37. 713
  38. 584
  39. 374
  40. 1235

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