You and a group of your friends are in the library. One friend says there is a 100 dollar bill hidden between pages 75 and 76 of a book in the library. But you decide not to go and look for it. Why?
You know that the odd number in a book is always on the right and the even number is always on the left. So, the page numbers you were given could not be facing each other. Therefore, you know for a fact that the money could not be hidden there.