A bookworm can chew through a millimiter (mm) of paper or cardboard in half an hour. One day it encounters a particularly tasty treat: a two-volume edition of a large book standing on a shelf as shown.

The volumes are identical in size, each has a front and a back cover that is a millimeter thick on each side, and the pages of each are a 10mm thick stack of paper from the first page to the last.

If a bookworm starts its meal on the first page of the first volume (already inside the front cover), how long will it take to eat his way through to the last page of the second volume (inside the second volume’s back cover)?

Ordinarily a two volume book set is set on a shelf with the first volume on the left meaning that page one is on the right side of the left volume and that the last page of the second volume is on the left side of the right volume. That means simply has to eat through the front cover of the first volume and the back cover of the second volume. Since each of these is a millimeter thick, and the worm eats at 2 mm per hour, the answer is just 1 hour!

Posted by Eric on 2003-10-22 21:24:50