Based on this video.
Here’s the situation. You’re in a jungle. You’ve accidentally eaten a poisonous mushroom. But you know how to get the antidote. There’s a species of frog that lives in the jungle and if you lick one it’s an antidote for the poison. And the frogs have no problem being caught or licked.
The problem is only female frogs produce the antidote. Licking a male frog does you no harm but it doesn’t help you either. And male and female frogs look identical. The only readily discernible difference between them is male frogs make a croaking sound which females do not. Males and females occur in equal numbers and there’s no pattern to their grouping or their croaking.
You’re lucky. You see a stump twenty feet ahead of you with a lone frog sitting on top of it. But then you hear a frog croaking behind you. You turn and see two frogs sitting on a rock twenty feet behind you. You can tell it was one of those two frogs which croaked but you can’t tell which one. There are no other frogs in the area.
You start to get dizzy and you realize you only have enough time to walk to either the stump or the rock before you pass out and die. You can go to the stump and lick that frog or go to the rock and lick both frogs. So which one do you go to?
My answer:It doesn’t matter. You have a 50/50 chance either way. There’s a 50% chance the frog on the stump is female. There are two frogs on the rock but you know one of them is a male even if you don’t know which one it is. So essentially you have a single frog which might be female and that gives you the same 50% chance.
Here’s the official answer:You should go to the rock because you have better odds. There are four possible groupings of two frogs: FF, FM, MF, MM. You heard the croak so you know this pair isn’t FF. But of the remaining three groupings, two contain at least one female. So your odds are 2/3 in your favor.