Guesstimation
Weinstein, L., & Adam, J. A. (2008). Guesstimation: Solving the world's problems on the back of a cocktail napkin. Princeton, N.J.: Princeton University Press.
This is a fun book, demonstrating how just a few simple principles can give approximate answers to puzzling questions. How far does a soccer player run during an average game? How many people are picking their noses right now? And if all the people on earth were crammed together in one place, how much space would they occupy? What fi we gave each person a house and a small plot of land.
To figure these things out you need some basic information, but no worry: Weinstein and Adam tell you how to estimate even that information. A great book, useful too. Students would be far better off if they learned these estimation techniques than some of the other stuff that they are forced to memorize which will never be of value later on; Estimation skills are always valuable.
(Answers: the players run around 20km or 12 miles; ten million people are picking their nose (so stop it!). Everyone would fit (but uncomfortably) into a city whose land area was the size of Los Angeles. To give everyone a home would still only fill up 1% of the earth's surface)