# SAT Math Multiple Choice Question 857: Answer and Explanation

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**Question: 857**

**2.** As the elevation above sea level increases, the corresponding air pressure decreases.A scatterplot comparing elevation, in feet, to air pressure, as a percent of sea levelpressure, is shown below.

Air pressure is sometimes measured in inches of mercury. If sea level air pressuremeasures as 29.2 inches of mercury, what is the approximate difference, in inchesof mercury, between the pressure at sea level and the pressure at the death zone threshold?

- A. 7.6
- B. 10.2
- C. 19.0
- D. 21.6

**Correct Answer:** C

**Explanation:**

**C**

**Difficulty:** Medium

**Category:** Problem Solving and Data Analysis / Scatterplots

**Strategic Advice:** When questions are presented in a "set," you can sometimes use your answer from the previous question to answer the next one. However, make sure you answer the *right* question.

**Getting to the Answer:** You need to find the difference between the two indicated pressures. You know that the air pressure at the death zone threshold is approximately 35% of sea level air pressure from the previous question. Find 35% of 29.2 by multiplying: 0.35 × 29.2 = 10.2. Be careful here, as the question asks for the difference between this pressure and sea level pressure, which is 29.2 - 10.2 = 19.0. (C) is the correct answer.