Thread: Islander problem

You are on an island with three tribes. One always tells the truth, one always lies, and one gives an answer randomly (like a flip of a coin, truth or lie)..


What are TWO (if possible) yes or no questions that you can direct to two different tribe members or to the same tribe member to determine which way to go..

Originally Posted by zhupolongjoe

You are on an island with three tribes. One always tells the truth, one always lies, and one gives an answer randomly (like a flip of a coin, truth or lie)..


What are TWO (if possible) yes or no questions that you can direct to two different tribe members or to the same tribe member to determine which way to go..

?? Wouldn't that depend on which way you want to go?

It would depend who you asked right? If you asked the tribe that always told the truth, then you would get a reasonable answer (e.g. suppose you want to get North). So you could ask the same question twice.

Maybe it wasn't clear. One road leads to heaven, one to hell. You want heaven.


The three tribes are indistinguishable. What are two questions to ask?

Originally Posted by zhupolongjoe

Maybe it wasn't clear. One road leads to heaven, one to hell. You want heaven.


The three tribes are indistinguishable. What are two questions to ask?

1. Are you a liar for saying that road A leads to heaven?

2. Are you telling the truth for saying that road B leads to hell?

Can you explain that? What if the random guy is answering that, how will you know. Doesn't sound correct to me, but maybe with some explanation,

to make it simple, you've got a, b and c. They live on an island, therefore they know each other.
If there were just a liar and a truth talker you could ask what the other guy would say.

we are talking about three tribes
Therefore you might ask:
if I ask x people from tribe a, y people from tribe, z people from tribe c ...

In this way using the fact of numbers to ask a repetuous question...

And, because of the fact that the half-half tribe would awnser the question 50% of the times truthfully (with a margin of error) this is also checkable for x, y, z large

As I said, not there yet...