SAT Math Multiple Choice Question 411: Answer and Explanation

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Question: 411


The Lake Pontchartrain Causeway Bridge in Louisiana is the longest bridge in the United States, at 23.83 miles long. The histogram above shows the distribution of the lengths, in miles, of 28 of the longest bridges in the United States, including Lake Pontchartrain Causeway Bridge. Which of the following could be the median length of the 28 bridges represented in the histogram?

  • A. 5.9
  • B. 7.9
  • C. 9.2
  • D. 9.9

Correct Answer: B



Difficulty: Medium

Category: Problem Solving and Data Analysis / Statistics and Probability

Strategic Advice: The median of a data set is the middle value when the data points are arranged from least to greatest (or greatest to least). When there is an even number of data points, the median is the average of the two middle values.

Getting to the Answer: The histogram represents the lengths of 28 bridges, so the median length is the average of the 14th and 15th longest bridges. Because the number of bridges that are less than 6 miles long is 12, and the number of bridges that are less than 9 miles long is 12 + 8 + 20, the median length of the 28 bridges must be between 6 and 9 miles (because 14 and 15 lie between 12 and 20). Of the choices given, only (B) matches this criterion.

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