Consider the set of northwestern states or provinces {Montana, Washington, Idaho, Oregon, Alaska, British Columbia, Alberta}. If a person chooses one element, show that in three yes or no questions, we can determine the element.
a) Ask, "Is it in the first 3 ?"
If answer is yes, ask "Is it in the first 2 ?"
If the answer to that is Yes, the third question will determine which one
If the answer to No, then Idaho was it
if the answer to a) is NO
it must be in the last 4, split them into 2 pairs and ask
"is it in the first pair ?"
the third question would be to pick a member of the remaining pair.