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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 599 · 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. 1.159 + 348 =
  2. 2.832 − 601 =
  3. 3.815 − 237 =
  4. 4.927 − 258 =
  5. 5.599 − 143 =
  6. 6.766 − 231 =
  7. 7.782 + 457 =
  8. 8.801 − 475 =
  9. 9.622 + 579 =
  10. 10.576 − 385 =
  11. 11.835 − 585 =
  12. 12.247 + 452 =
  13. 13.747 − 308 =
  14. 14.847 − 596 =
  15. 15.926 − 568 =
  16. 16.826 − 722 =
  17. 17.858 − 288 =
  18. 18.206 + 391 =
  19. 19.737 − 163 =
  20. 20.498 + 139 =
  21. 21.718 + 435 =
  22. 22.537 + 396 =
  23. 23.810 − 672 =
  24. 24.772 + 201 =
  25. 25.626 + 121 =
  26. 26.289 + 338 =
  27. 27.243 + 315 =
  28. 28.763 − 257 =
  29. 29.741 − 576 =
  30. 30.636 + 153 =
  31. 31.284 + 501 =
  32. 32.621 − 132 =
  33. 33.793 − 223 =
  34. 34.301 + 468 =
  35. 35.609 + 571 =
  36. 36.138 + 297 =
  37. 37.387 + 283 =
  38. 38.292 + 574 =
  39. 39.567 + 407 =
  40. 40.698 + 258 =

Answer key

  1. 507
  2. 231
  3. 578
  4. 669
  5. 456
  6. 535
  7. 1239
  8. 326
  9. 1201
  10. 191
  11. 250
  12. 699
  13. 439
  14. 251
  15. 358
  16. 104
  17. 570
  18. 597
  19. 574
  20. 637
  21. 1153
  22. 933
  23. 138
  24. 973
  25. 747
  26. 627
  27. 558
  28. 506
  29. 165
  30. 789
  31. 785
  32. 489
  33. 570
  34. 769
  35. 1180
  36. 435
  37. 670
  38. 866
  39. 974
  40. 956

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