A bookworm starts at the outside of the front cover of volume I of a certain set of books and eats his way to the outside of the back cover of volume III.
If each volume is one inch thick, how much distance did the bookworm travel?
Answer
The bookworm travelled a distance of one inch and not three inches.
If you look at the arrangement of the books, the back cover of volume I is on the left and the front cover of volume I is on the right and next to the back cover of volume II. Likewise, the back cover of volume III is on the left and the front cover of volume III is on the right.
The distance between the front cover of volume I to the back cover of volume III is only one inch, which is the thickness of volume II.