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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 988 · 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. 1.791 − 173 =
  2. 2.508 + 178 =
  3. 3.449 + 124 =
  4. 4.930 − 334 =
  5. 5.747 + 261 =
  6. 6.528 − 347 =
  7. 7.755 − 337 =
  8. 8.598 + 589 =
  9. 9.686 + 494 =
  10. 10.248 + 362 =
  11. 11.635 + 529 =
  12. 12.985 − 155 =
  13. 13.185 + 625 =
  14. 14.217 + 443 =
  15. 15.505 + 431 =
  16. 16.607 + 484 =
  17. 17.148 + 418 =
  18. 18.612 + 536 =
  19. 19.678 − 436 =
  20. 20.733 − 149 =
  21. 21.362 + 414 =
  22. 22.849 − 537 =
  23. 23.491 − 211 =
  24. 24.134 + 381 =
  25. 25.605 + 635 =
  26. 26.736 + 484 =
  27. 27.470 + 463 =
  28. 28.387 + 283 =
  29. 29.938 − 431 =
  30. 30.391 + 511 =
  31. 31.508 − 162 =
  32. 32.785 − 131 =
  33. 33.660 + 186 =
  34. 34.949 − 569 =
  35. 35.638 + 343 =
  36. 36.305 + 542 =
  37. 37.722 + 528 =
  38. 38.825 − 263 =
  39. 39.274 + 224 =
  40. 40.548 − 343 =

Answer key

  1. 618
  2. 686
  3. 573
  4. 596
  5. 1008
  6. 181
  7. 418
  8. 1187
  9. 1180
  10. 610
  11. 1164
  12. 830
  13. 810
  14. 660
  15. 936
  16. 1091
  17. 566
  18. 1148
  19. 242
  20. 584
  21. 776
  22. 312
  23. 280
  24. 515
  25. 1240
  26. 1220
  27. 933
  28. 670
  29. 507
  30. 902
  31. 346
  32. 654
  33. 846
  34. 380
  35. 981
  36. 847
  37. 1250
  38. 562
  39. 498
  40. 205

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