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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 898 · 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. 1.591 + 638 =
  2. 2.358 + 397 =
  3. 3.622 + 498 =
  4. 4.722 + 441 =
  5. 5.269 + 336 =
  6. 6.396 + 622 =
  7. 7.438 − 331 =
  8. 8.883 − 199 =
  9. 9.347 + 228 =
  10. 10.935 − 315 =
  11. 11.552 − 232 =
  12. 12.703 − 342 =
  13. 13.630 − 497 =
  14. 14.610 − 118 =
  15. 15.917 − 755 =
  16. 16.747 − 386 =
  17. 17.627 − 154 =
  18. 18.277 + 583 =
  19. 19.372 + 181 =
  20. 20.763 − 159 =
  21. 21.709 + 665 =
  22. 22.532 − 219 =
  23. 23.601 − 491 =
  24. 24.560 − 187 =
  25. 25.581 − 476 =
  26. 26.208 + 484 =
  27. 27.769 + 535 =
  28. 28.734 + 186 =
  29. 29.428 + 587 =
  30. 30.537 − 343 =
  31. 31.291 + 342 =
  32. 32.730 + 261 =
  33. 33.648 + 182 =
  34. 34.188 + 471 =
  35. 35.312 + 159 =
  36. 36.602 − 307 =
  37. 37.645 + 175 =
  38. 38.579 + 251 =
  39. 39.987 − 588 =
  40. 40.843 − 361 =

Answer key

  1. 1229
  2. 755
  3. 1120
  4. 1163
  5. 605
  6. 1018
  7. 107
  8. 684
  9. 575
  10. 620
  11. 320
  12. 361
  13. 133
  14. 492
  15. 162
  16. 361
  17. 473
  18. 860
  19. 553
  20. 604
  21. 1374
  22. 313
  23. 110
  24. 373
  25. 105
  26. 692
  27. 1304
  28. 920
  29. 1015
  30. 194
  31. 633
  32. 991
  33. 830
  34. 659
  35. 471
  36. 295
  37. 820
  38. 830
  39. 399
  40. 482

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