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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 239 · 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. 1.791 − 279 =
  2. 2.787 + 143 =
  3. 3.830 − 638 =
  4. 4.559 − 441 =
  5. 5.782 − 585 =
  6. 6.133 + 444 =
  7. 7.722 − 618 =
  8. 8.282 + 469 =
  9. 9.903 − 597 =
  10. 10.780 − 264 =
  11. 11.915 − 505 =
  12. 12.201 + 506 =
  13. 13.232 + 375 =
  14. 14.558 + 131 =
  15. 15.834 − 638 =
  16. 16.428 + 558 =
  17. 17.727 + 355 =
  18. 18.880 − 263 =
  19. 19.521 + 431 =
  20. 20.621 − 426 =
  21. 21.629 − 487 =
  22. 22.644 − 208 =
  23. 23.720 + 302 =
  24. 24.339 + 321 =
  25. 25.191 + 549 =
  26. 26.552 − 321 =
  27. 27.733 + 179 =
  28. 28.133 + 251 =
  29. 29.551 − 308 =
  30. 30.638 − 187 =
  31. 31.569 + 481 =
  32. 32.749 − 621 =
  33. 33.431 + 524 =
  34. 34.327 + 441 =
  35. 35.814 − 359 =
  36. 36.247 + 182 =
  37. 37.318 + 497 =
  38. 38.270 + 388 =
  39. 39.834 − 158 =
  40. 40.512 − 338 =

Answer key

  1. 512
  2. 930
  3. 192
  4. 118
  5. 197
  6. 577
  7. 104
  8. 751
  9. 306
  10. 516
  11. 410
  12. 707
  13. 607
  14. 689
  15. 196
  16. 986
  17. 1082
  18. 617
  19. 952
  20. 195
  21. 142
  22. 436
  23. 1022
  24. 660
  25. 740
  26. 231
  27. 912
  28. 384
  29. 243
  30. 451
  31. 1050
  32. 128
  33. 955
  34. 768
  35. 455
  36. 429
  37. 815
  38. 658
  39. 676
  40. 174

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