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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 639 · 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. 1.361 + 639 =
  2. 2.383 + 282 =
  3. 3.469 − 132 =
  4. 4.794 − 312 =
  5. 5.777 − 303 =
  6. 6.709 + 265 =
  7. 7.584 + 269 =
  8. 8.965 − 823 =
  9. 9.753 − 342 =
  10. 10.971 − 269 =
  11. 11.284 + 169 =
  12. 12.734 − 629 =
  13. 13.985 − 431 =
  14. 14.602 − 235 =
  15. 15.789 − 331 =
  16. 16.266 + 262 =
  17. 17.892 − 467 =
  18. 18.310 + 339 =
  19. 19.381 + 394 =
  20. 20.476 + 633 =
  21. 21.635 + 277 =
  22. 22.154 + 386 =
  23. 23.496 + 231 =
  24. 24.857 − 352 =
  25. 25.439 − 214 =
  26. 26.318 + 525 =
  27. 27.912 − 484 =
  28. 28.612 − 227 =
  29. 29.379 + 536 =
  30. 30.866 − 291 =
  31. 31.487 − 211 =
  32. 32.574 − 441 =
  33. 33.679 + 588 =
  34. 34.251 + 504 =
  35. 35.669 + 544 =
  36. 36.686 − 286 =
  37. 37.543 − 269 =
  38. 38.478 + 491 =
  39. 39.131 + 466 =
  40. 40.549 − 283 =

Answer key

  1. 1000
  2. 665
  3. 337
  4. 482
  5. 474
  6. 974
  7. 853
  8. 142
  9. 411
  10. 702
  11. 453
  12. 105
  13. 554
  14. 367
  15. 458
  16. 528
  17. 425
  18. 649
  19. 775
  20. 1109
  21. 912
  22. 540
  23. 727
  24. 505
  25. 225
  26. 843
  27. 428
  28. 385
  29. 915
  30. 575
  31. 276
  32. 133
  33. 1267
  34. 755
  35. 1213
  36. 400
  37. 274
  38. 969
  39. 597
  40. 266

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