A woman drives an SUV that gets 13 ​mi/gal (mpg). Her husband drives a hybrid that gets 65 mpg.

Question

A woman drives an SUV that gets

13

​mi/gal (mpg). Her husband drives a hybrid that gets

65

mpg. Every​ week, they travel the same number of miles. They want to improve their combined mpg. They have two options on how they can improve it.

Option​ 1: They can tune the SUV and increase its mileage by

2

mpg and keep the hybrid as it is.

Option​ 2: They can buy a new hybrid that gets

85

mpg and keep the SUV as it is.

Which option will give them a better combined​ mpg?

Compute the combined mpg for each option.

Which option will give a better combined​ mpg?

Answer 1

1

MPG = 2D/(D/(13+2)+D/65) = 2/(1/15+1/65) = 2/(16/195) = 195/8 = 24 3/8

2

MPG = 2D/(D/13+D/(65+20)) = 2/(1/13+1/85) = 1105/49 = 22 27/49

Option 1 has better MPG