Assume there are 100 million passenger cars in the united states and the average fuel efficiency is 21 mi/gal of gasoline. if the average distance traveled by each car is 12,600 mi/yr, how much gasoline would be saved per year if average fuel efficiency could be increased to 28 mi/gal?

15 billions gallons are saved a year with the fuel efficiency increased to 28 mi/gal.

Step-by-step explanation:

This problem can be solved by the use of rules of three.

The first step is find how many gallons are used with the efficiency of 21mi/gal:

1gal are used for 21 miles. How many gal are needed for 12,600 miles. So

1 gal - 21 miles

x gal - 12,600 miles

21x = 12,600

x = 600 gallons

Each passenger uses 600 gallons a year.

There are 100 million passengers a year, so:

1 passenger - 600 gallons

100,000,000 passengers - x gallons

x = 600*100,000,000

x = 60,000,000,000

With the efficiency at 21mi/gal, 60 billion gallons are used a year.

Now with the efficiency at 28 mi/gal

Same logic as above:

1gal - 28 miles

x gal - 12,600 miles

28x = 12,600

x = 450 gallons

Each passenger uses 450 gallons a year of gasoline.

There are 100 million passengers a year, so:

1 passenger - 450 gallons

100,000,000 passengers - x gallons

x = 450*100,000,000

x = 45,000,000,000

With the efficiency at 28mi/gal, 45 billion gallons are used a year. It means that 60 billion - 45 billion = 15 billions gallons are saved a year with the fuel efficiency increased to 28 mi/gal.

salary

step-by-step explanation:

the height of the surface increases from the center out to the sides of the road.

step-by-step explanation:

as we move out we move away from the x-axis.

and as mentioned in the problem statement that height of a road increases when we move away from the center x.

hence proved that 3rd option

the height of the surface increases from the center out to the sides of the road.

is the correct option.