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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 279 · 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. 1.664 − 331 =
  2. 2.449 + 664 =
  3. 3.343 + 116 =
  4. 4.507 − 299 =
  5. 5.537 − 381 =
  6. 6.711 − 187 =
  7. 7.498 + 575 =
  8. 8.701 + 251 =
  9. 9.711 − 404 =
  10. 10.470 − 161 =
  11. 11.719 + 129 =
  12. 12.139 + 625 =
  13. 13.965 − 366 =
  14. 14.506 − 151 =
  15. 15.127 + 223 =
  16. 16.701 + 377 =
  17. 17.200 + 317 =
  18. 18.405 + 296 =
  19. 19.174 + 226 =
  20. 20.773 + 184 =
  21. 21.598 − 124 =
  22. 22.592 + 473 =
  23. 23.381 + 519 =
  24. 24.225 + 371 =
  25. 25.727 + 475 =
  26. 26.832 − 117 =
  27. 27.744 − 587 =
  28. 28.730 + 301 =
  29. 29.457 + 494 =
  30. 30.159 + 571 =
  31. 31.745 − 611 =
  32. 32.478 + 275 =
  33. 33.256 + 369 =
  34. 34.629 − 227 =
  35. 35.916 − 631 =
  36. 36.152 + 487 =
  37. 37.498 − 145 =
  38. 38.769 − 168 =
  39. 39.726 + 625 =
  40. 40.427 + 591 =

Answer key

  1. 333
  2. 1113
  3. 459
  4. 208
  5. 156
  6. 524
  7. 1073
  8. 952
  9. 307
  10. 309
  11. 848
  12. 764
  13. 599
  14. 355
  15. 350
  16. 1078
  17. 517
  18. 701
  19. 400
  20. 957
  21. 474
  22. 1065
  23. 900
  24. 596
  25. 1202
  26. 715
  27. 157
  28. 1031
  29. 951
  30. 730
  31. 134
  32. 753
  33. 625
  34. 402
  35. 285
  36. 639
  37. 353
  38. 601
  39. 1351
  40. 1018

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