A set of three volumes of The History of Hungary sit on a book shelf. Each volume is 5cm thick. A very hungry caterpillar starts at the outside of the front cover of volume one and eats her way through to the
outside of the back cover of volume three. After a wee nap and more than a little dyspepsia, the caterpillar pauses to consider how far she has travelled through the books.
Assuming she travelled in a straight line, can you work out how far she travelled through the books?