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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 1 · 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. 1.635 + 581 =
  2. 2.817 − 672 =
  3. 3.285 + 165 =
  4. 4.859 − 751 =
  5. 5.141 + 176 =
  6. 6.709 + 236 =
  7. 7.763 − 642 =
  8. 8.284 + 481 =
  9. 9.280 + 436 =
  10. 10.704 − 121 =
  11. 11.544 − 192 =
  12. 12.928 − 408 =
  13. 13.502 − 224 =
  14. 14.226 + 439 =
  15. 15.688 + 602 =
  16. 16.843 − 552 =
  17. 17.594 + 269 =
  18. 18.391 + 311 =
  19. 19.726 + 261 =
  20. 20.864 − 692 =
  21. 21.475 + 218 =
  22. 22.515 − 189 =
  23. 23.657 + 272 =
  24. 24.804 − 377 =
  25. 25.436 − 145 =
  26. 26.988 − 116 =
  27. 27.608 + 441 =
  28. 28.734 + 603 =
  29. 29.437 − 219 =
  30. 30.218 + 245 =
  31. 31.316 + 255 =
  32. 32.807 − 434 =
  33. 33.736 − 288 =
  34. 34.253 + 168 =
  35. 35.490 − 176 =
  36. 36.756 + 651 =
  37. 37.487 − 211 =
  38. 38.560 + 166 =
  39. 39.631 − 351 =
  40. 40.592 − 152 =

Answer key

  1. 1216
  2. 145
  3. 450
  4. 108
  5. 317
  6. 945
  7. 121
  8. 765
  9. 716
  10. 583
  11. 352
  12. 520
  13. 278
  14. 665
  15. 1290
  16. 291
  17. 863
  18. 702
  19. 987
  20. 172
  21. 693
  22. 326
  23. 929
  24. 427
  25. 291
  26. 872
  27. 1049
  28. 1337
  29. 218
  30. 463
  31. 571
  32. 373
  33. 448
  34. 421
  35. 314
  36. 1407
  37. 276
  38. 726
  39. 280
  40. 440

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