SAT Math Multiple Choice Question 38: Answer and Explanation

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Question: 38

8.

Five samples of each of three different rock types were collected on a hiking trip in Colorado. Each sample was analyzed for its gold content. The milligrams of gold found in each sample are presented in the table above. What is the percent difference of the average gold content in the granite samples when compared to the average gold content of the gneiss samples?

  • A. The gold content in the gneiss samples is 62% higher than the gold content in the granite samples.
  • B. The gold content in the granite samples is 62% higher than the gold content in the gneiss samples.
  • C. The gold content in the gneiss samples is 87% higher than the gold content in the granite samples.
  • D. The gold content in the granite samples is 87% higher than the gold content in the gneiss samples.

Correct Answer: D

Explanation:

D The average gold content in the granite samples can be calculated as follows:

The average gold content in the gneiss samples can be calculated as

Because the average gold content in the granite samples is higher, you can eliminate (A) and (C). Ballpark to find the right answer. 0.782 is almost twice as much as 0.418. Therefore, granite contains, on average, almost 100% more gold than gneiss does. The correct answer is (D).

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