#### Answer

$2.74\times 10^8$ gallons of gasoline are used each day in the USA.

#### Work Step by Step

We can use 300 million people as the population.
Then the number of cars is 200 million.
For each car, we can find the average number of miles driven each day.
(10,000 miles / year)(1 year/ 365 days) = 27.40 miles/day
For each car, we can find the average number of gallons used each day.
(27.40 miles/day)(1 gallon/20 miles) = 1.37 gallons/day
We can find the total number of gallons used each day by 200 million cars.
(200 million)(1.37 gallons/day) = 274 million gallons/day
$2.74\times 10^8$ gallons of gasoline are used each day in the USA.