How thick is a billion page book?

Answer 1

Of course, there is no such thing as a billion page book. However, doing a quick estimate, 100 pages is in the order of 1 cm. (the exact width might depend on the thickness of the paper), so that gives you about 10,000 pages per meter. A million pages would then use up 100 meters, and a billion (short scale, i.e., a thousand million) would give you 100 kilometers.