Isaac is a physical therapist who specializes in leg injuries. His patients differ in age and type of injury.
The probability that a patient is 46-80 years old is 0.05, the probability that a patient suffers from shin pain is 0.23, and the probability that a patient is 46-80 years old and suffers from shin pain is 0.04.
What is the probability that a randomly chosen patient is 46-80 years old or suffers from shin pain?

Given:

An airport limo service charges riders a fixed charge of $15 plus  $4.00 per mile.

To find:

Distance in miles must a rider go to have an  average cost per mile of $4.60.

Solution:

Let x be the number of miles the rider travel.

Total charges = Fixed charges + Variable charges

According to the question,

Fixed charges = $15

Variable charges = $4x

So,  total charges

Divide the total charges by number of miles to get the cost per mile.

Average cost per mile is $4.60.

Divide both sides by 0.60.

Therefore, the required number of miles is 25.