Gasoline varies in cost from $0.97 to $1.17 per gallon. If a car’s mileage varies from 16 to 24 miles per gallon, what is the difference between the most and least that the gasoline for a 480-mile trip will cost?  Choose the correct choice from the following choices.
A) $15.07 B) $15.23 C) $15.50 D) $15.70 E) $15.72
Solution:   We know that the per gallon cost of gasoline varies from $0.97 - $1.17.   Now we want to find the MAXIMUM difference between the least amount of money spent on gasoline and the largest amount of money spent i.e. to calculate max. trip cost - min. trip cost.   Mileage is given to be 16 to 24 miles per gallon, thus to travel 480 miles you will need gasoline in the range 480/24 to 480/16 which is 20 to 30 gallons.   So, for these 20 gallons and 30 gallons of gasoline the cost is as follows: (divide this task into 2 parts, 1 for 30 gallons and 2nd one for 20 gallons).   Case 1: for 30 gallons the cost is 30*0.97 to 30*1.17 which is $29.10 to $35.10   Case 2: for 20 gallons the cost is 20*0.97 to 20*1.17 which is $19.40 to $23.40   Thus, the maximum cost of the 480 mile trip is $35.10 and minimum is $19.40   so the difference is $35.10 - $19.40 = $15.70   Answer: $15.70 35.10 -  19.40= 
<gadget id="calculator"> 35.10 -  19.40</gadget>
<output>15.7</output>
$15.70   Answer: $15.70
<result>D</result>
Gasoline varies in cost from $0.97 to $1.17 per gallon. If a car’s mileage varies from 16 to 24 miles per gallon, what is the difference between the most and least that the gasoline for a 480-mile trip will cost?