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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 92 · 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. 1.595 − 451 =
  2. 2.522 + 139 =
  3. 3.651 + 645 =
  4. 4.705 − 465 =
  5. 5.776 + 668 =
  6. 6.653 − 256 =
  7. 7.220 + 643 =
  8. 8.810 − 474 =
  9. 9.608 − 204 =
  10. 10.524 + 226 =
  11. 11.771 − 171 =
  12. 12.651 − 216 =
  13. 13.705 + 324 =
  14. 14.617 + 357 =
  15. 15.450 + 219 =
  16. 16.669 + 383 =
  17. 17.273 + 178 =
  18. 18.203 + 231 =
  19. 19.598 − 285 =
  20. 20.364 + 375 =
  21. 21.298 + 318 =
  22. 22.181 + 118 =
  23. 23.360 + 328 =
  24. 24.508 − 338 =
  25. 25.779 + 391 =
  26. 26.811 − 607 =
  27. 27.471 − 153 =
  28. 28.591 + 321 =
  29. 29.131 + 324 =
  30. 30.369 + 475 =
  31. 31.323 + 689 =
  32. 32.720 + 511 =
  33. 33.696 + 345 =
  34. 34.908 − 543 =
  35. 35.179 + 645 =
  36. 36.569 + 257 =
  37. 37.440 − 286 =
  38. 38.254 + 423 =
  39. 39.965 − 389 =
  40. 40.566 − 223 =

Answer key

  1. 144
  2. 661
  3. 1296
  4. 240
  5. 1444
  6. 397
  7. 863
  8. 336
  9. 404
  10. 750
  11. 600
  12. 435
  13. 1029
  14. 974
  15. 669
  16. 1052
  17. 451
  18. 434
  19. 313
  20. 739
  21. 616
  22. 299
  23. 688
  24. 170
  25. 1170
  26. 204
  27. 318
  28. 912
  29. 455
  30. 844
  31. 1012
  32. 1231
  33. 1041
  34. 365
  35. 824
  36. 826
  37. 154
  38. 677
  39. 576
  40. 343

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