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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 577 · 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. 1.217 + 121 =
  2. 2.518 + 165 =
  3. 3.280 + 686 =
  4. 4.641 + 584 =
  5. 5.576 − 346 =
  6. 6.312 + 511 =
  7. 7.787 − 665 =
  8. 8.669 + 534 =
  9. 9.621 − 382 =
  10. 10.361 + 472 =
  11. 11.630 − 406 =
  12. 12.311 + 482 =
  13. 13.617 + 155 =
  14. 14.417 − 227 =
  15. 15.393 + 438 =
  16. 16.493 − 368 =
  17. 17.464 − 181 =
  18. 18.539 − 393 =
  19. 19.522 − 377 =
  20. 20.816 − 228 =
  21. 21.420 + 271 =
  22. 22.426 + 541 =
  23. 23.904 − 294 =
  24. 24.432 − 229 =
  25. 25.577 + 211 =
  26. 26.850 − 746 =
  27. 27.296 + 521 =
  28. 28.399 + 406 =
  29. 29.511 + 221 =
  30. 30.593 − 121 =
  31. 31.443 − 126 =
  32. 32.448 − 254 =
  33. 33.483 + 472 =
  34. 34.569 − 211 =
  35. 35.703 − 324 =
  36. 36.701 + 551 =
  37. 37.240 + 264 =
  38. 38.456 − 331 =
  39. 39.655 + 378 =
  40. 40.433 + 268 =

Answer key

  1. 338
  2. 683
  3. 966
  4. 1225
  5. 230
  6. 823
  7. 122
  8. 1203
  9. 239
  10. 833
  11. 224
  12. 793
  13. 772
  14. 190
  15. 831
  16. 125
  17. 283
  18. 146
  19. 145
  20. 588
  21. 691
  22. 967
  23. 610
  24. 203
  25. 788
  26. 104
  27. 817
  28. 805
  29. 732
  30. 472
  31. 317
  32. 194
  33. 955
  34. 358
  35. 379
  36. 1252
  37. 504
  38. 125
  39. 1033
  40. 701

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