PSAT Math Multiple-Choice Question 376: Answer and Explanation

Question: 376

Engine oil often contains zinc, which reduces engine wear. Company A's oil contains 4 percent zinc and company B's oil contains 9 percent. Suppose a car uses 8 pints of company B's oil and a truck uses 6 quarts of company A's oil. How many times more zinc is in the car's oil than in the truck's? (1 quart = 2 pints)

• A. 0.34
• B. 0.67
• C. 1.5
• D. 3

Correct Answer: C

Explanation:

C

Difficulty: Hard

Category: Unit Conversion

Getting to the Answer: It's easiest to compare two amounts when they are written in the same units, so start by converting the car's pints to quarts and then go from there. The conversion from pints to quarts is straightforward:

Next, find the amount of zinc in each car using the percent formula: Percent × whole = part. Write the percents as decimals and multiply:

Car: 0.09 × 4 quarts = 0.36 quarts of zinc

Truck: 0.04 × 6 quarts = 0.24 quarts of zinc

Finally, compare the amount in the car to the amount in the truck: . The car has 1.5 times as much zinc in its oil as the truck, which is (C).