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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 804 · 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. 1.235 + 415 =
  2. 2.153 + 576 =
  3. 3.516 + 563 =
  4. 4.466 − 229 =
  5. 5.540 − 253 =
  6. 6.739 − 135 =
  7. 7.533 + 413 =
  8. 8.724 + 313 =
  9. 9.775 − 637 =
  10. 10.352 + 531 =
  11. 11.458 + 626 =
  12. 12.496 − 175 =
  13. 13.276 + 401 =
  14. 14.175 + 644 =
  15. 15.240 + 623 =
  16. 16.557 − 426 =
  17. 17.607 + 209 =
  18. 18.677 − 261 =
  19. 19.450 − 268 =
  20. 20.250 + 199 =
  21. 21.783 − 624 =
  22. 22.712 + 232 =
  23. 23.821 − 473 =
  24. 24.450 − 186 =
  25. 25.757 + 344 =
  26. 26.503 − 154 =
  27. 27.503 + 224 =
  28. 28.278 + 531 =
  29. 29.562 + 151 =
  30. 30.836 − 115 =
  31. 31.171 + 242 =
  32. 32.588 + 462 =
  33. 33.397 + 675 =
  34. 34.678 − 475 =
  35. 35.547 − 178 =
  36. 36.606 + 458 =
  37. 37.487 − 247 =
  38. 38.741 + 121 =
  39. 39.485 − 273 =
  40. 40.729 + 232 =

Answer key

  1. 650
  2. 729
  3. 1079
  4. 237
  5. 287
  6. 604
  7. 946
  8. 1037
  9. 138
  10. 883
  11. 1084
  12. 321
  13. 677
  14. 819
  15. 863
  16. 131
  17. 816
  18. 416
  19. 182
  20. 449
  21. 159
  22. 944
  23. 348
  24. 264
  25. 1101
  26. 349
  27. 727
  28. 809
  29. 713
  30. 721
  31. 413
  32. 1050
  33. 1072
  34. 203
  35. 369
  36. 1064
  37. 240
  38. 862
  39. 212
  40. 961

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