Question

1.which of the following would save more fuel?

a.Replacing a compact car that gets 34 per gallon(mpg)with a hybrid that gets 54 mpg
b.Replacing a sport utility(SUV)that gets 18 mpg with a sedan that gets 28 mpg
c.Both changes would save the same amount of fuel.
2.Explain your reasoning for your choice.

Answer 1

9514 1404 393

Answer:

1. b

2. For each 1000 miles driven, (a) saves 10.9 gallons, while (b) saves 19.8 gallons

Explanation:

The fuel savings will depend on the miles driven. If we use 1000 miles as the reference, the various vehicle fuel usages are ...

gallons = miles/(miles/gallon)

18 mpg: 1000/18 = 55.6 gallons

28 mpg: 1000/28 = 35.7 gallons

34 mpg: 1000/34 = 29.4 gallons

54 mpg: 1000/54 = 18.5 gallons

So, ...

replacing 34 mpg with 54 mpg saves 29.4 -18.5 = 10.9 gallons.

replacing 18 mpg with 28 mpg saves 55.6 -35.7 ≈ 19.8 gallons.

Replacing the SUV with a sedan saves more fuel, assuming all vehicles are driven the same distance.

__

The fuel use reduction from 18 mpg to 28 mpg is about 36%, whereas from 34 mpg to 54 mpg. the reduction is about 37%. The SUV replacement is a better choice because the smaller fraction of a much larger fuel use is still more savings than obtained by replacing the compact car.