Question

CAN SOMEONE PLEASE HELP ME WITH THIS QUESTION?!?!?!?!?!?!!?!!!!!!
Make an order of magnitude calculation of the number of gallons of gasoline used by Americans each year.
1. List all of your assumptions about the facts you will need
2. show all equations that you used
3. explain all the steps you used

Answer 1

Here's how I did it, using only what I already know (or think I know): the population of the US is about 300 million, of whom 70% or so work. Assume the average worker drives a car 10,000 miles a year and that car averages 20 MPG. I get 3x10^8 * 0.70 * 10000 miles / 20 MPG = 10^11 gallons of gasoline.

Now we turn to the actual numbers, here:

http://www.eia.gov/energyexplained/index.cfm?page=gasoline_use

And the government claims the US usese 360 million gallons per day in 2011, which is 360 million x 365 = 1.3 x 10^11 gallons. So I was bang on, which is a little surprising.