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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 681 · 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. 1.430 − 151 =
  2. 2.481 + 427 =
  3. 3.700 − 436 =
  4. 4.668 − 381 =
  5. 5.842 − 168 =
  6. 6.452 + 226 =
  7. 7.952 − 631 =
  8. 8.953 − 547 =
  9. 9.533 + 144 =
  10. 10.630 + 235 =
  11. 11.488 − 365 =
  12. 12.453 + 665 =
  13. 13.931 − 236 =
  14. 14.692 + 346 =
  15. 15.331 + 656 =
  16. 16.955 − 762 =
  17. 17.297 + 241 =
  18. 18.729 − 198 =
  19. 19.870 − 342 =
  20. 20.471 − 327 =
  21. 21.761 − 361 =
  22. 22.233 + 113 =
  23. 23.229 + 393 =
  24. 24.501 + 588 =
  25. 25.324 + 581 =
  26. 26.955 − 187 =
  27. 27.832 − 278 =
  28. 28.361 + 166 =
  29. 29.188 + 348 =
  30. 30.863 − 635 =
  31. 31.181 + 624 =
  32. 32.299 + 417 =
  33. 33.718 − 208 =
  34. 34.211 + 223 =
  35. 35.231 + 364 =
  36. 36.563 + 209 =
  37. 37.988 − 222 =
  38. 38.906 − 241 =
  39. 39.809 − 611 =
  40. 40.172 + 584 =

Answer key

  1. 279
  2. 908
  3. 264
  4. 287
  5. 674
  6. 678
  7. 321
  8. 406
  9. 677
  10. 865
  11. 123
  12. 1118
  13. 695
  14. 1038
  15. 987
  16. 193
  17. 538
  18. 531
  19. 528
  20. 144
  21. 400
  22. 346
  23. 622
  24. 1089
  25. 905
  26. 768
  27. 554
  28. 527
  29. 536
  30. 228
  31. 805
  32. 716
  33. 510
  34. 434
  35. 595
  36. 772
  37. 766
  38. 665
  39. 198
  40. 756

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