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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 900 · 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. 1.130 + 499 =
  2. 2.973 − 515 =
  3. 3.490 − 361 =
  4. 4.372 + 549 =
  5. 5.748 + 483 =
  6. 6.716 + 251 =
  7. 7.249 + 224 =
  8. 8.901 − 658 =
  9. 9.972 − 233 =
  10. 10.528 − 377 =
  11. 11.346 + 279 =
  12. 12.857 − 751 =
  13. 13.357 + 452 =
  14. 14.868 − 711 =
  15. 15.497 + 415 =
  16. 16.722 − 287 =
  17. 17.476 − 262 =
  18. 18.621 + 633 =
  19. 19.724 − 141 =
  20. 20.552 + 506 =
  21. 21.219 + 242 =
  22. 22.599 − 223 =
  23. 23.461 + 484 =
  24. 24.256 + 134 =
  25. 25.148 + 134 =
  26. 26.549 − 251 =
  27. 27.360 + 632 =
  28. 28.648 + 188 =
  29. 29.127 + 211 =
  30. 30.577 − 154 =
  31. 31.553 − 329 =
  32. 32.362 + 285 =
  33. 33.266 + 123 =
  34. 34.256 + 679 =
  35. 35.696 + 206 =
  36. 36.203 + 687 =
  37. 37.546 − 294 =
  38. 38.364 + 132 =
  39. 39.264 + 341 =
  40. 40.850 − 617 =

Answer key

  1. 629
  2. 458
  3. 129
  4. 921
  5. 1231
  6. 967
  7. 473
  8. 243
  9. 739
  10. 151
  11. 625
  12. 106
  13. 809
  14. 157
  15. 912
  16. 435
  17. 214
  18. 1254
  19. 583
  20. 1058
  21. 461
  22. 376
  23. 945
  24. 390
  25. 282
  26. 298
  27. 992
  28. 836
  29. 338
  30. 423
  31. 224
  32. 647
  33. 389
  34. 935
  35. 902
  36. 890
  37. 252
  38. 496
  39. 605
  40. 233

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