SAT Math Multiple Choice Question 520: Answer and Explanation

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Question: 520

10. When scuba divers ascend from deep water, they must either rise slowly or take safety breaks to avoid nitrogen buildup in their lungs. The length of time a diver should take to ascend is directly proportional to how many feet she needs to ascend. If a scuba diver can safely ascend 165 feet in 5.5 minutes, then how many feet can she ascend in 90 seconds?

  • A. 45
  • B. 60
  • C. 75
  • D. 90

Correct Answer: A

Explanation:

A

Difficulty: Medium

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

Strategic Advice: To answer a question that says "directly proportional," set two ratios equal to each other and solve for the missing amount. Don't forget—match the units in the numerators and in the denominators on both sides.

Getting to the Answer: Let f equal the number of feet that the diver can safely ascend in 90 seconds. Set up a proportion and solve for f. Because the first rate is given in terms of minutes, write 90 seconds as 1.5 minutes.

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