An empty fuel tank with a capacity of 200 gallons was filled partially with fuel A and then to capacity with fuel B. Fuel A contains 12% ethanol by volume and fuel B contains 16% ethanol by volume. If the full fuel tank contains 30 gallons of ethanol, how many gallons of fuel A were added?	Choose one
A) 160	B) 150	C) 100	D) 80	E) 50
Say there are A gallons of fuel A in the tank, then there would be 200-A gallons of fuel B.   The amount of ethanol in A gallons of fuel A is 0.12A;   The amount of ethanol in 200-A gallons of fuel B is 0.16(200-A);   Since the total amount of ethanol is 30 gallons then 0.12A+0.16(200-A)=30 --&gt; A=50.   Answer: 50.
<result>E</result>
An empty fuel tank with a capacity of 200 gallons was filled partially with fuel A and then to capacity with fuel B. Fuel A contains 12% ethanol by volume and fuel B contains 16% ethanol by volume. If the full fuel tank contains 30 gallons of ethanol, how many gallons of fuel A were added?