PSAT Math Multiple-Choice Question 203: Answer and Explanation

Question: 203

Crude oil is sold by the barrel, which refers to both the physical container and a unit of measure, abbreviated as bbl. One barrel holds 42 gallons and, consequently, 1 bbl =42 gallons. An oil company is filling an order for 2,500 barrels. The machine the company uses to fill the barrels pumps at a rate of 37.5 gallons per minute. If the oil company has 8 machines working simultaneously, how long will it take to fill all the barrels in the order?

• A. 5 hours and 50 minutes
• B. 12 hours and 45 minutes
• C. 28 hours and 30 minutes
• D. 46 hours and 40 minutes

Correct Answer: A

Explanation:

A

Difficulty: Medium

Category: Problem Solving and Data Analysis/Rates, Ratios, Proportions, and Percentages

Getting to the Answer: Let the units in this question guide you to the answer. You can do one conversion at a time or all of them at once. Just be sure to line up the units so they'll cancel correctly. The company uses 8 machines, each of which pumps at a rate of 37.5 gallons per minute, so the rate is actually 8 × 37.5 = 300 gallons per minute. Find the total number of gallons needed and then use the rate to find the time:

The answers are given in hours and minutes, so change 350 minutes to 350 ÷ 60 = 5.833 hours, which is 5 hours and 50 minutes. (A) is correct.