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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 629 · 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. 1.637 + 115 =
  2. 2.284 + 451 =
  3. 3.417 + 285 =
  4. 4.151 + 587 =
  5. 5.639 + 615 =
  6. 6.420 − 281 =
  7. 7.493 − 193 =
  8. 8.573 + 129 =
  9. 9.595 + 345 =
  10. 10.160 + 173 =
  11. 11.573 − 398 =
  12. 12.234 + 452 =
  13. 13.592 − 338 =
  14. 14.745 + 617 =
  15. 15.498 + 185 =
  16. 16.649 − 328 =
  17. 17.507 − 349 =
  18. 18.152 + 333 =
  19. 19.838 − 711 =
  20. 20.726 + 247 =
  21. 21.261 + 583 =
  22. 22.473 + 194 =
  23. 23.169 + 186 =
  24. 24.543 + 582 =
  25. 25.141 + 669 =
  26. 26.192 + 382 =
  27. 27.608 + 404 =
  28. 28.190 + 458 =
  29. 29.496 + 564 =
  30. 30.751 − 141 =
  31. 31.713 − 296 =
  32. 32.434 + 221 =
  33. 33.983 − 351 =
  34. 34.446 + 647 =
  35. 35.848 − 316 =
  36. 36.745 − 597 =
  37. 37.174 + 544 =
  38. 38.612 + 626 =
  39. 39.255 + 369 =
  40. 40.230 + 618 =

Answer key

  1. 752
  2. 735
  3. 702
  4. 738
  5. 1254
  6. 139
  7. 300
  8. 702
  9. 940
  10. 333
  11. 175
  12. 686
  13. 254
  14. 1362
  15. 683
  16. 321
  17. 158
  18. 485
  19. 127
  20. 973
  21. 844
  22. 667
  23. 355
  24. 1125
  25. 810
  26. 574
  27. 1012
  28. 648
  29. 1060
  30. 610
  31. 417
  32. 655
  33. 632
  34. 1093
  35. 532
  36. 148
  37. 718
  38. 1238
  39. 624
  40. 848

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