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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 751 · 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. 1.246 + 142 =
  2. 2.175 + 417 =
  3. 3.157 + 401 =
  4. 4.517 + 135 =
  5. 5.724 + 548 =
  6. 6.470 + 161 =
  7. 7.880 − 551 =
  8. 8.543 − 132 =
  9. 9.655 − 408 =
  10. 10.455 + 227 =
  11. 11.617 + 404 =
  12. 12.666 + 661 =
  13. 13.546 + 219 =
  14. 14.171 + 625 =
  15. 15.604 − 276 =
  16. 16.928 − 234 =
  17. 17.673 − 265 =
  18. 18.874 − 534 =
  19. 19.175 + 165 =
  20. 20.600 + 125 =
  21. 21.687 + 264 =
  22. 22.646 + 122 =
  23. 23.544 − 145 =
  24. 24.613 − 303 =
  25. 25.305 + 548 =
  26. 26.719 + 429 =
  27. 27.130 + 151 =
  28. 28.789 + 431 =
  29. 29.711 − 164 =
  30. 30.188 + 186 =
  31. 31.508 + 137 =
  32. 32.481 − 328 =
  33. 33.607 − 199 =
  34. 34.151 + 192 =
  35. 35.546 − 135 =
  36. 36.814 − 121 =
  37. 37.564 + 514 =
  38. 38.816 − 366 =
  39. 39.593 − 206 =
  40. 40.588 + 481 =

Answer key

  1. 388
  2. 592
  3. 558
  4. 652
  5. 1272
  6. 631
  7. 329
  8. 411
  9. 247
  10. 682
  11. 1021
  12. 1327
  13. 765
  14. 796
  15. 328
  16. 694
  17. 408
  18. 340
  19. 340
  20. 725
  21. 951
  22. 768
  23. 399
  24. 310
  25. 853
  26. 1148
  27. 281
  28. 1220
  29. 547
  30. 374
  31. 645
  32. 153
  33. 408
  34. 343
  35. 411
  36. 693
  37. 1078
  38. 450
  39. 387
  40. 1069

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