PSAT Math Multiple-Choice Question 200: Answer and Explanation

Question: 200

Kudzu is a vine-like plant that grows indigenously in Asia. It was brought over to the United States in the early 20th century to help combat soil erosion. As can often happen when foreign species are introduced into a non-native habitat, kudzu growth exploded and it became invasive. In one area of Virginia, kudzu covered approximately 3,200 acres of a farmer's cropland, so the farmer tried a new herbicide. After two weeks of use, 2,800 acres of the cropland were free of the kudzu. Based on these results, and assuming the same general conditions, how many of the 30,000 acres of kudzu-infested cropland in that region would still be covered if all the farmers in the entire region had used the herbicide?

• A. 3,750
• B. 4,000
• C. 26,000
• D. 26,250

Correct Answer: A

Explanation:

A

Difficulty: Medium

Category: Problem Solving and Data Analysis/-Statistics and Probability

Getting to the Answer: This is a science crossover question. Read the first three sentences quickly—they are simply describing the context. The second half of the paragraph poses the question, so read that more carefully. In the sample, 2,800 out of 3,200 acres were free of kudzu after applying the herbicide. This is of the area. For the whole region, assuming the same general conditions, 0.875(30,000) = 26,250 acres should be free of the kudzu. Be careful—this is not the answer. The question asks how much of the cropland would still be covered by kudzu, so subtract to get 30,000 - 26,250 = 3,750 acres. (A) is correct.