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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 538 · 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. 1.142 + 617 =
  2. 2.165 + 292 =
  3. 3.467 + 261 =
  4. 4.226 + 137 =
  5. 5.517 + 206 =
  6. 6.420 − 312 =
  7. 7.575 + 591 =
  8. 8.456 + 643 =
  9. 9.788 + 641 =
  10. 10.926 − 459 =
  11. 11.193 + 225 =
  12. 12.749 − 471 =
  13. 13.562 + 654 =
  14. 14.877 − 496 =
  15. 15.515 + 523 =
  16. 16.515 − 205 =
  17. 17.303 + 338 =
  18. 18.155 + 175 =
  19. 19.400 + 584 =
  20. 20.675 + 221 =
  21. 21.431 − 268 =
  22. 22.504 − 242 =
  23. 23.901 − 141 =
  24. 24.537 + 388 =
  25. 25.125 + 401 =
  26. 26.700 + 535 =
  27. 27.845 − 302 =
  28. 28.332 + 221 =
  29. 29.300 + 121 =
  30. 30.358 + 673 =
  31. 31.573 + 336 =
  32. 32.659 − 128 =
  33. 33.723 + 189 =
  34. 34.450 − 331 =
  35. 35.403 + 566 =
  36. 36.272 + 681 =
  37. 37.537 − 355 =
  38. 38.547 + 226 =
  39. 39.934 − 437 =
  40. 40.480 − 189 =

Answer key

  1. 759
  2. 457
  3. 728
  4. 363
  5. 723
  6. 108
  7. 1166
  8. 1099
  9. 1429
  10. 467
  11. 418
  12. 278
  13. 1216
  14. 381
  15. 1038
  16. 310
  17. 641
  18. 330
  19. 984
  20. 896
  21. 163
  22. 262
  23. 760
  24. 925
  25. 526
  26. 1235
  27. 543
  28. 553
  29. 421
  30. 1031
  31. 909
  32. 531
  33. 912
  34. 119
  35. 969
  36. 953
  37. 182
  38. 773
  39. 497
  40. 291

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