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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 513 · 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. 1.640 + 519 =
  2. 2.828 − 701 =
  3. 3.642 − 243 =
  4. 4.647 − 134 =
  5. 5.561 − 369 =
  6. 6.428 + 599 =
  7. 7.700 − 335 =
  8. 8.480 + 261 =
  9. 9.728 + 687 =
  10. 10.566 − 207 =
  11. 11.421 − 271 =
  12. 12.390 + 472 =
  13. 13.363 + 381 =
  14. 14.536 + 469 =
  15. 15.818 − 149 =
  16. 16.755 + 636 =
  17. 17.941 − 263 =
  18. 18.171 + 521 =
  19. 19.531 + 567 =
  20. 20.177 + 338 =
  21. 21.744 + 245 =
  22. 22.724 + 292 =
  23. 23.490 − 121 =
  24. 24.755 + 617 =
  25. 25.632 + 496 =
  26. 26.340 + 485 =
  27. 27.686 − 578 =
  28. 28.529 − 112 =
  29. 29.797 − 514 =
  30. 30.634 + 314 =
  31. 31.505 − 345 =
  32. 32.981 − 262 =
  33. 33.772 − 168 =
  34. 34.587 − 123 =
  35. 35.158 + 488 =
  36. 36.391 + 269 =
  37. 37.703 + 478 =
  38. 38.785 + 466 =
  39. 39.634 − 522 =
  40. 40.532 − 192 =

Answer key

  1. 1159
  2. 127
  3. 399
  4. 513
  5. 192
  6. 1027
  7. 365
  8. 741
  9. 1415
  10. 359
  11. 150
  12. 862
  13. 744
  14. 1005
  15. 669
  16. 1391
  17. 678
  18. 692
  19. 1098
  20. 515
  21. 989
  22. 1016
  23. 369
  24. 1372
  25. 1128
  26. 825
  27. 108
  28. 417
  29. 283
  30. 948
  31. 160
  32. 719
  33. 604
  34. 464
  35. 646
  36. 660
  37. 1181
  38. 1251
  39. 112
  40. 340

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