Question

If the US population was 200,000,000 and the cost of fuel was $2.00 per Litre and petrol mileage is 20 km/litre and you buy every single person in the US a $2,000 car and enough fuel to run it nonstop at 20 mph for a year: How much money would you spend?

Answer 1

Let's count how much money we will spend for 1 person during a year driving his car :

20 [miles/h] × 1.6 [km/mile] × 8760 [hours/year] × 1/20 [litr/km] × 2 $/litr = $28032
Where 1/20 [litr/km] is how much fuel a car needs to drive 1 km
And 1.6 is a coefficient between miles and kilometers.
Then we add the cost of a car for 1 person and multiply this sum on 2×10⁸ population :
2 × 10⁸ × ($2000 + $28032) = $6 × 10¹²