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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 706 · 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. 1.607 + 136 =
  2. 2.758 + 341 =
  3. 3.493 + 456 =
  4. 4.693 + 535 =
  5. 5.542 − 321 =
  6. 6.708 − 148 =
  7. 7.471 + 493 =
  8. 8.178 + 562 =
  9. 9.686 + 541 =
  10. 10.963 − 621 =
  11. 11.710 + 238 =
  12. 12.241 + 363 =
  13. 13.929 − 588 =
  14. 14.617 + 128 =
  15. 15.161 + 554 =
  16. 16.428 + 451 =
  17. 17.811 − 438 =
  18. 18.637 + 587 =
  19. 19.810 − 682 =
  20. 20.601 + 371 =
  21. 21.795 − 511 =
  22. 22.843 − 558 =
  23. 23.753 − 493 =
  24. 24.424 + 361 =
  25. 25.689 + 373 =
  26. 26.299 + 528 =
  27. 27.548 − 124 =
  28. 28.789 − 533 =
  29. 29.223 + 173 =
  30. 30.984 − 125 =
  31. 31.144 + 555 =
  32. 32.527 + 401 =
  33. 33.524 − 242 =
  34. 34.280 + 364 =
  35. 35.649 + 475 =
  36. 36.135 + 645 =
  37. 37.533 − 425 =
  38. 38.723 − 115 =
  39. 39.661 − 172 =
  40. 40.524 − 179 =

Answer key

  1. 743
  2. 1099
  3. 949
  4. 1228
  5. 221
  6. 560
  7. 964
  8. 740
  9. 1227
  10. 342
  11. 948
  12. 604
  13. 341
  14. 745
  15. 715
  16. 879
  17. 373
  18. 1224
  19. 128
  20. 972
  21. 284
  22. 285
  23. 260
  24. 785
  25. 1062
  26. 827
  27. 424
  28. 256
  29. 396
  30. 859
  31. 699
  32. 928
  33. 282
  34. 644
  35. 1124
  36. 780
  37. 108
  38. 608
  39. 489
  40. 345

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