A bookworm eats from the first page of an encyclopedia to the last page.

logic/bookworm

Problem

A bookworm eats from the first page of an encyclopedia to the last
page.  The bookworm eats in a straight line.  The encyclopedia consists
of ten 1000-page volumes and is sitting on a bookshelf in the usual
order.  Not counting covers, title pages, etc., how many pages does the
bookworm eat through?

Show solution

On a book shelf the first page of the first volume is on the "inside"
  __                             __
B|  |                           |  |F
A|1 |...........................|10|R
C|  |                           |  |O
K|  |                           |  |N
 |  |                           |  |T
  ----------------------------------
so the bookworm eats only through the cover of the first volume, then 8 times
1000 pages of Volumes 2 - 9, then through the cover to the 1st page of Vol 10.
He eats 8,000 pages.

If the bookworm ate the first page and the last page, it ate 8,004 pages.