How is this true? Bookworm puzzle This is from Eugene Northrop's book Riddles in Mathematics. 
Why is the answer 1 inch. Iit should be three. What logic am I missing here?


I think according to the picture, the "front cover of volume I" is actually between the books I and II, while the back cover of volume 3 is between II and III.  I think the wording is just trying to mislead the reader to think the worm eats through all the books, when it really just eats through volume II (which is the only thing between the outside of the front cover of volume I and the outside of the back cover of volume III).
