Here's my favorite:
3) There are three books on a shelf. the front cover of each book is 1/2 inch. the back cover of each book is also 1/2 inch. the paper between total 1 inch in each book. A bookworm is eating its way through the books. If the bookworm begins from the front page of book #1 and eats through until the back page of book #3, how many inches has the bookworm ate through?