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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 321 · 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. 1.658 + 214 =
  2. 2.259 + 365 =
  3. 3.935 − 653 =
  4. 4.418 − 175 =
  5. 5.455 + 404 =
  6. 6.837 − 576 =
  7. 7.127 + 562 =
  8. 8.733 − 611 =
  9. 9.425 + 458 =
  10. 10.707 − 363 =
  11. 11.913 − 366 =
  12. 12.552 + 294 =
  13. 13.601 + 614 =
  14. 14.788 − 374 =
  15. 15.206 + 267 =
  16. 16.695 + 291 =
  17. 17.235 + 277 =
  18. 18.489 − 358 =
  19. 19.749 + 625 =
  20. 20.788 + 328 =
  21. 21.657 + 368 =
  22. 22.554 − 132 =
  23. 23.475 + 291 =
  24. 24.960 − 324 =
  25. 25.290 + 202 =
  26. 26.614 + 377 =
  27. 27.304 + 129 =
  28. 28.585 + 554 =
  29. 29.725 − 451 =
  30. 30.213 + 529 =
  31. 31.675 + 568 =
  32. 32.746 − 273 =
  33. 33.738 − 224 =
  34. 34.257 + 221 =
  35. 35.716 + 462 =
  36. 36.746 − 367 =
  37. 37.634 + 345 =
  38. 38.578 − 293 =
  39. 39.360 + 338 =
  40. 40.909 − 388 =

Answer key

  1. 872
  2. 624
  3. 282
  4. 243
  5. 859
  6. 261
  7. 689
  8. 122
  9. 883
  10. 344
  11. 547
  12. 846
  13. 1215
  14. 414
  15. 473
  16. 986
  17. 512
  18. 131
  19. 1374
  20. 1116
  21. 1025
  22. 422
  23. 766
  24. 636
  25. 492
  26. 991
  27. 433
  28. 1139
  29. 274
  30. 742
  31. 1243
  32. 473
  33. 514
  34. 478
  35. 1178
  36. 379
  37. 979
  38. 285
  39. 698
  40. 521

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