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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 17 · 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. 1.551 + 194 =
  2. 2.257 + 554 =
  3. 3.676 + 214 =
  4. 4.465 − 114 =
  5. 5.639 − 145 =
  6. 6.551 + 611 =
  7. 7.661 + 405 =
  8. 8.198 + 171 =
  9. 9.771 + 274 =
  10. 10.340 + 451 =
  11. 11.719 − 209 =
  12. 12.622 − 141 =
  13. 13.680 − 271 =
  14. 14.309 + 343 =
  15. 15.821 − 557 =
  16. 16.285 + 244 =
  17. 17.214 + 434 =
  18. 18.311 + 282 =
  19. 19.781 + 139 =
  20. 20.618 + 479 =
  21. 21.958 − 429 =
  22. 22.505 − 391 =
  23. 23.862 − 392 =
  24. 24.431 + 417 =
  25. 25.747 − 176 =
  26. 26.459 − 319 =
  27. 27.494 − 369 =
  28. 28.477 − 138 =
  29. 29.718 + 385 =
  30. 30.660 + 247 =
  31. 31.670 + 168 =
  32. 32.318 + 193 =
  33. 33.539 − 421 =
  34. 34.654 + 194 =
  35. 35.700 − 177 =
  36. 36.661 + 202 =
  37. 37.778 + 426 =
  38. 38.873 − 387 =
  39. 39.546 − 332 =
  40. 40.776 + 597 =

Answer key

  1. 745
  2. 811
  3. 890
  4. 351
  5. 494
  6. 1162
  7. 1066
  8. 369
  9. 1045
  10. 791
  11. 510
  12. 481
  13. 409
  14. 652
  15. 264
  16. 529
  17. 648
  18. 593
  19. 920
  20. 1097
  21. 529
  22. 114
  23. 470
  24. 848
  25. 571
  26. 140
  27. 125
  28. 339
  29. 1103
  30. 907
  31. 838
  32. 511
  33. 118
  34. 848
  35. 523
  36. 863
  37. 1204
  38. 486
  39. 214
  40. 1373

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