PSAT Math Multiple-Choice Question 357: Answer and Explanation

Question: 357

Ethanol can be mixed with gasoline to reduce automobile emissions. Much automotive gasoline is 15 percent ethanol by volume. An oil company tries decreasing the ethanol content to 6 percent to lower the cost. If a car with a 14-gallon tank is filled with the 15 percent blend and a second car with a 10-gallon tank is filled with the 6 percent blend, how many times more ethanol is in the first car than in the second car?

• A. 1.5
• B. 2.5
• C. 3.5
• D. 4.0

Correct Answer: C

Explanation:

C

Difficulty: Medium

Category: Percents

Getting to the Answer: Starting with the 14--gallon tank, plug the known values into the three-part -formula: 15% × 14 =? → 0.15 × 14 = 2.1 gallons of ethanol. Repeat for the smaller tank: 6% × 10 =? → 0.06 × 10 = 0.6 gallons of ethanol. The question asks how many times more ethanol is in the larger tank, so divide the quantities to get . This matches (C).