A spy wanted to get into a secret club for some information.

But to enter you had to know there’s a secret password.

He waits outside and spies on two members.

When Member 1 knocks on the door, the guard knocks back 6 times and the member replies with 3 knocks and he was let in.

When member 2 knocks on the door, the guard knocks 12 times and the member replies with 6 knocks and he was let in.

So the spy thought he had cracked the logic so he knocked on the door.

The guard knocked ten times and the spy replied with 5 knocks but he was not let in.

What was the correct secret password and what’s the logic behind it?