It's a funny story, but they screwed up the riddle. You need to know the answer to a yes/no question that this liar/truth-teller can answer. For example, whic

It's a funny story, but they screwed up the riddle. You need to know the answer to a yes/no question that this liar/truth-teller can answer. For example, which road should I take to get to the castle? You only have one question, so you can't ask are you a tree-frog, because then you wouldn't know which road to take. http://mathforum.org/dr.math/faq/faq.liar.html http://mathforum.org/dr.math/faq/faq.liar.html