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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 451 · 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. 1.211 + 475 =
  2. 2.632 + 613 =
  3. 3.675 − 126 =
  4. 4.897 − 766 =
  5. 5.707 − 347 =
  6. 6.376 + 204 =
  7. 7.786 + 677 =
  8. 8.288 + 266 =
  9. 9.253 + 177 =
  10. 10.937 − 343 =
  11. 11.844 − 134 =
  12. 12.579 − 294 =
  13. 13.798 − 421 =
  14. 14.461 + 598 =
  15. 15.600 − 374 =
  16. 16.426 + 669 =
  17. 17.475 + 231 =
  18. 18.470 − 361 =
  19. 19.440 − 197 =
  20. 20.195 + 298 =
  21. 21.522 − 288 =
  22. 22.518 + 397 =
  23. 23.717 + 177 =
  24. 24.649 − 245 =
  25. 25.788 − 121 =
  26. 26.681 + 402 =
  27. 27.318 + 311 =
  28. 28.666 − 216 =
  29. 29.132 + 624 =
  30. 30.534 + 205 =
  31. 31.584 + 465 =
  32. 32.357 + 526 =
  33. 33.598 − 399 =
  34. 34.183 + 621 =
  35. 35.204 + 549 =
  36. 36.269 + 582 =
  37. 37.464 − 342 =
  38. 38.726 + 584 =
  39. 39.942 − 653 =
  40. 40.685 − 216 =

Answer key

  1. 686
  2. 1245
  3. 549
  4. 131
  5. 360
  6. 580
  7. 1463
  8. 554
  9. 430
  10. 594
  11. 710
  12. 285
  13. 377
  14. 1059
  15. 226
  16. 1095
  17. 706
  18. 109
  19. 243
  20. 493
  21. 234
  22. 915
  23. 894
  24. 404
  25. 667
  26. 1083
  27. 629
  28. 450
  29. 756
  30. 739
  31. 1049
  32. 883
  33. 199
  34. 804
  35. 753
  36. 851
  37. 122
  38. 1310
  39. 289
  40. 469

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