Mr. Harper's car used 5 gallons of gasoline to travel 150 miles. After he had some work done on the cars engine, it used it used 6 gallons of gasoline to travel 210 miles. If the price of gasoline was $3.50 per gallon, how much money did Mr. Harper save per mile after the work was done on the cars engine? (Round your answers to the nearest cent.)

He saves $0.0175 per mile

Step-by-step explanation:

Before the work done on the car's engine, it took 0.033 gallons to travel one mile (5 gallons / 150miles = 0.033). After this work, the car spends 0.028 gallons to travel one mile (6 gallons/210 miles = 0.028). The difference between this two is:

0.033 gallons/mile-0.028 gallons/mile = 0.005 gallons per mile.

Now Mr. Harper's saves 0.005 gallons per mile.

In money he saves:

$3,50/gallon*0.005 gallon/mile = $0.0175/mile (the unit of "gallon" cancel each other)

Rounded to the nearest cent:

He saves $0.0 per mile.