How many liters of water are swallowed by the people living in the United States in one year? This is a type of problem made famous by Enrico Fermi (1901-1954), who was a master at this sort of back-of-the-envelope calculation. Such problems are often called Fermi problems in his honor. (1 liter = 10-3 m3 1 quart.) Estimate the population to be about 3 x 10^8 people each drinking about 1.5 L/day