I came across this question in a Mental Ability Test. The question is as follows —
Anita, a girl, goes to a party. Entry into the party requires a special passcode. In order to know the passcode she listens to the conversation between the guard and two people.
In the first conversation between the guard and the man, the guard says $12$ and the man says $6$ and he is granted entry.
In the next dialogue between the guard and the lady the guard says $6$ and the woman says $3$ and then she is granted entry.
Then Anita thinking she has got the passcode goes to the guard. The guard says $10$ and Anita says $5$ but the guard says "You are wrong!" and denied her entry.
What should Anita have said to gain entry?
I have no idea on how to solve this problem.