If I interpret this bizarre setup correctly, then when she finds herself being interviewed, there are three possibilities:1) it's Monday and it landed heads2) it's Monday and it landed tails3) it's Tuesday and it landed tailsIt's a fair coin, so the probability of #1 and #2 are equal; #3 occurs if and only if #2 occurs, so the probability of #2 and #3 are equal.Since all three are equally probable and only one has the coins landing heads, the answer is 1/3.This is an odd restatement of other well-known questions that restrict the problem space to 3/4 of the possible outcomes, such as:You two children are in a house and at least one is a boy. You knock on the door and a boy answers. What is the probability that the other child is a boy?(Answer: 1/3) |