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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 615 · 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. 1.167 + 261 =
  2. 2.178 + 373 =
  3. 3.734 + 135 =
  4. 4.589 + 545 =
  5. 5.482 + 114 =
  6. 6.736 + 198 =
  7. 7.265 + 551 =
  8. 8.525 + 189 =
  9. 9.769 − 557 =
  10. 10.971 − 484 =
  11. 11.808 − 286 =
  12. 12.648 + 353 =
  13. 13.635 − 346 =
  14. 14.924 − 529 =
  15. 15.789 − 326 =
  16. 16.695 + 323 =
  17. 17.787 + 591 =
  18. 18.512 − 337 =
  19. 19.533 − 195 =
  20. 20.740 − 161 =
  21. 21.777 + 408 =
  22. 22.810 − 141 =
  23. 23.928 − 576 =
  24. 24.912 − 636 =
  25. 25.398 + 404 =
  26. 26.797 − 319 =
  27. 27.293 + 247 =
  28. 28.713 − 482 =
  29. 29.788 − 334 =
  30. 30.217 + 681 =
  31. 31.416 + 279 =
  32. 32.755 − 175 =
  33. 33.618 − 301 =
  34. 34.280 + 502 =
  35. 35.830 − 247 =
  36. 36.446 − 293 =
  37. 37.178 + 431 =
  38. 38.652 + 143 =
  39. 39.669 + 688 =
  40. 40.371 + 144 =

Answer key

  1. 428
  2. 551
  3. 869
  4. 1134
  5. 596
  6. 934
  7. 816
  8. 714
  9. 212
  10. 487
  11. 522
  12. 1001
  13. 289
  14. 395
  15. 463
  16. 1018
  17. 1378
  18. 175
  19. 338
  20. 579
  21. 1185
  22. 669
  23. 352
  24. 276
  25. 802
  26. 478
  27. 540
  28. 231
  29. 454
  30. 898
  31. 695
  32. 580
  33. 317
  34. 782
  35. 583
  36. 153
  37. 609
  38. 795
  39. 1357
  40. 515

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