You and two buddies are in a diner. The hostess asks you, "Does everyone want coffee?" You say, "I do not know." Your friend Anna says: "I do not know." Finally, your friend Jo says, "No, not everyone wants coffee." The hostess comes back and gives coffee to the people who want it. How did she figure out who wanted coffee?
You said I do not know
That means you want coffee but you don't know about the rest. That's how.
She brings coffee to the two who said I do not know and the last one says no not everyone, so he doesn't want any
Thats my solution atleast.
I agree, better explanation:
She ask "Does everyone want coffee?" If someone says no, they don't want coffee and essentially saying not EVERYONE wants coffee, if they say IDK, that's a yes, but they can't speak for everyone else so it's a IDK.
Only works if the first two say IDK. Kinda a silly riddle contingent on literal wording.