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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 711 · 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. 1.172 + 199 =
  2. 2.947 − 285 =
  3. 3.423 − 119 =
  4. 4.951 − 346 =
  5. 5.210 + 631 =
  6. 6.893 − 789 =
  7. 7.373 + 542 =
  8. 8.394 + 674 =
  9. 9.123 + 479 =
  10. 10.571 − 169 =
  11. 11.543 + 459 =
  12. 12.332 + 576 =
  13. 13.412 + 182 =
  14. 14.437 − 314 =
  15. 15.506 − 367 =
  16. 16.330 + 161 =
  17. 17.641 + 347 =
  18. 18.948 − 437 =
  19. 19.610 − 503 =
  20. 20.811 − 302 =
  21. 21.315 + 149 =
  22. 22.938 − 464 =
  23. 23.424 − 141 =
  24. 24.637 + 495 =
  25. 25.931 − 246 =
  26. 26.888 − 735 =
  27. 27.745 + 514 =
  28. 28.250 + 189 =
  29. 29.500 + 652 =
  30. 30.968 − 189 =
  31. 31.214 + 112 =
  32. 32.232 + 362 =
  33. 33.543 − 378 =
  34. 34.310 + 517 =
  35. 35.213 + 431 =
  36. 36.983 − 872 =
  37. 37.751 + 139 =
  38. 38.570 + 455 =
  39. 39.555 + 674 =
  40. 40.691 − 567 =

Answer key

  1. 371
  2. 662
  3. 304
  4. 605
  5. 841
  6. 104
  7. 915
  8. 1068
  9. 602
  10. 402
  11. 1002
  12. 908
  13. 594
  14. 123
  15. 139
  16. 491
  17. 988
  18. 511
  19. 107
  20. 509
  21. 464
  22. 474
  23. 283
  24. 1132
  25. 685
  26. 153
  27. 1259
  28. 439
  29. 1152
  30. 779
  31. 326
  32. 594
  33. 165
  34. 827
  35. 644
  36. 111
  37. 890
  38. 1025
  39. 1229
  40. 124

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