how would you approach this?

Assume 320 million people, average of 4 people and one car (15 gallons) per household. So 80 million cars on the road with a total tank capacity of 210 million gallons of oil at any given moment.

US 300,000,000 Population

Assume the average # of times someone decides to use an airplane is 1 Total # of people using planes = 300,000,000 Daily # of people using planes = 300M/365 = ~820,000 people using a plane ~820,000/200 (capacity of a plane) = 41,000 planes fly out a day planes fly for 18 hours a day

so 41,000 / 18 = ~2,000 planes flying

Market size for oil in the US is 18 million barrels consumed per day. America uses 100 quadrillion BTUs of energy per year, 40 of which come from oil, 20 from coal, 20 from natgas, 10 from nuclear, 3 from hydro, 7 from other sources.

This is very basic stuff that a strong candidate will be able to cite off the top of his head- along with other economic information.

what about industrial use of oil and airplanes?

That's included in the 18 mmbpd figure. You also have heating oil, plastics, electricity (mostly in Hawaii), refining losses (5%), marine fuel oil, tar/asphalt for road construction, butane/propane, and more.

I think only 13 mmbpd of the total 18 is actually used on the road. The rest is used for aviation, chemicals, heating, and electricity.

Obviously all you have to demonstrate in questions like these is sound thought process

illini, I really like your method, and would probably use the same method if I knew this data, but I'm trying to get a general way to approach these questions so can I say:

for Oil, we need to consider oil use that is residential and commercial Let's look at residential first:

300M people in us, average of 3 people per household = 100M households assume 1/2 of all households have a car, so 50M households have a car, average household has 1.5 cars, so 100M cars. each car uses 5 gallons a week 500M gallons/week assume 50 weeks in a year 25B gallons a year. This is only residential use, assume residential use only represents 50% of all oil use. So total consumption is 50B gallons of oil a year.

Sure, but the guy interviewing behind you will be able to cite the 18 mmbpd figure, give him the eia.doe.gov website for interviewer as your source, and then ask him if he wants to know how many deepwater rigs it takes to produce that with a wry grin on his face. Which is why I'd probably ask a question where having a basic economic stat might be helpful but wouldn't make the question trivial.

Energy consumption stats are just as important as other economic figures like the GDP, unemployment rate, or earnings on the S&P 500. You should have them memorized. Aside from unemployment, they don't change that quickly.

They don't care if you get it right, it's about your thought process. The fact that you came on here to ask isn't a good sign.