Man has 3 coins. One coin has a head on each side. Second coin has tails on both sides. Third coin has head and tails on it. All coins are same denomination. Man places all three coins in pocket, selects one and shows you one side. It is a head. He is willing Tibet you even money that it is the two headed coin , you win if it is the normal coin. His reasoning is that it can't be the two tsiled coin since a head is showing therefore there is a 50/50chance of it being the two headed coin. Would this be a good bet for me? Why or why not?