Use of applied mathematics during hiring process for developers

Please solve a task. We have 5 similar coins, 3 of those are real and weight the same, while 2 are fake. 1 fake coin is lighter and the other is heavier than the real ones. How many weighting operations we will need to find at least one real coin?

  1. 2
  2. 3
  3. p
  4. 3
  5. at least 3, maximum 4
  6. 2
  7. 1
  8. Your problem statement is flawed. I can discover both coins by weighing each of 4 coins. If I discover the 'odd' coins in the first three, I can stop then.
  9. 2
  10. Don't know
  11. 3
  12. -
  13. 2
  14. 2 - but it will fail if both fake coins weight the same as 2 good ones
  15. 3 worst case 2 best case
  16. 3
  17. At most 2
  18. 3
  19. 1 or 2