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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 222 · 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. 1.659 + 139 =
  2. 2.831 − 501 =
  3. 3.522 + 395 =
  4. 4.677 − 217 =
  5. 5.632 − 177 =
  6. 6.655 − 189 =
  7. 7.182 + 131 =
  8. 8.281 + 626 =
  9. 9.592 + 532 =
  10. 10.534 − 205 =
  11. 11.230 + 663 =
  12. 12.932 − 653 =
  13. 13.519 − 368 =
  14. 14.256 + 313 =
  15. 15.776 − 372 =
  16. 16.596 − 258 =
  17. 17.481 + 115 =
  18. 18.515 − 374 =
  19. 19.510 − 381 =
  20. 20.650 − 413 =
  21. 21.851 − 732 =
  22. 22.317 + 337 =
  23. 23.419 + 267 =
  24. 24.634 − 419 =
  25. 25.541 − 424 =
  26. 26.539 − 273 =
  27. 27.555 − 342 =
  28. 28.309 + 409 =
  29. 29.309 + 298 =
  30. 30.647 + 323 =
  31. 31.730 + 554 =
  32. 32.691 + 542 =
  33. 33.643 + 591 =
  34. 34.416 − 262 =
  35. 35.409 + 336 =
  36. 36.325 + 512 =
  37. 37.432 + 641 =
  38. 38.709 + 564 =
  39. 39.434 + 374 =
  40. 40.608 + 658 =

Answer key

  1. 798
  2. 330
  3. 917
  4. 460
  5. 455
  6. 466
  7. 313
  8. 907
  9. 1124
  10. 329
  11. 893
  12. 279
  13. 151
  14. 569
  15. 404
  16. 338
  17. 596
  18. 141
  19. 129
  20. 237
  21. 119
  22. 654
  23. 686
  24. 215
  25. 117
  26. 266
  27. 213
  28. 718
  29. 607
  30. 970
  31. 1284
  32. 1233
  33. 1234
  34. 154
  35. 745
  36. 837
  37. 1073
  38. 1273
  39. 808
  40. 1266

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