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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 68 · 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. 1.940 − 641 =
  2. 2.539 + 131 =
  3. 3.321 + 171 =
  4. 4.454 + 223 =
  5. 5.540 + 351 =
  6. 6.295 + 652 =
  7. 7.441 + 671 =
  8. 8.313 + 133 =
  9. 9.656 + 234 =
  10. 10.286 + 141 =
  11. 11.586 + 142 =
  12. 12.497 + 331 =
  13. 13.980 − 564 =
  14. 14.206 + 512 =
  15. 15.457 + 512 =
  16. 16.621 + 271 =
  17. 17.977 − 388 =
  18. 18.448 − 141 =
  19. 19.289 + 687 =
  20. 20.721 + 141 =
  21. 21.646 − 185 =
  22. 22.430 − 126 =
  23. 23.418 + 667 =
  24. 24.854 − 182 =
  25. 25.247 + 117 =
  26. 26.814 − 329 =
  27. 27.979 − 156 =
  28. 28.747 + 413 =
  29. 29.304 + 442 =
  30. 30.205 + 286 =
  31. 31.322 + 457 =
  32. 32.693 + 473 =
  33. 33.151 + 514 =
  34. 34.730 + 315 =
  35. 35.480 − 141 =
  36. 36.205 + 339 =
  37. 37.368 + 603 =
  38. 38.351 + 636 =
  39. 39.734 + 511 =
  40. 40.186 + 476 =

Answer key

  1. 299
  2. 670
  3. 492
  4. 677
  5. 891
  6. 947
  7. 1112
  8. 446
  9. 890
  10. 427
  11. 728
  12. 828
  13. 416
  14. 718
  15. 969
  16. 892
  17. 589
  18. 307
  19. 976
  20. 862
  21. 461
  22. 304
  23. 1085
  24. 672
  25. 364
  26. 485
  27. 823
  28. 1160
  29. 746
  30. 491
  31. 779
  32. 1166
  33. 665
  34. 1045
  35. 339
  36. 544
  37. 971
  38. 987
  39. 1245
  40. 662

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