PSAT Math Multiple-Choice Practice Question 546

Question: 546

Scientists say the ability to run fast helps animals outrun predators and catch prey. The table below shows the distance, in kilometers, covered in 10 minutes (min) of running for several mammals from Africa.

Average Speeds of African Mammals

AnimalDistance covered in 10 min of running
African wild dog12 km
Cheetah18 km
Elephant7 km
Giraffe9 km
Lion14 km
Zebra11 km

Which of the following mammals covers a distance closest to the combined distance covered by a cheetah running for 15 min and a giraffe running for 5 min?

Correct Answer: A

Explanation:

A

The question asks for the animal running for a specified period of time that covers a distance that is equivalent to the sum of two other animals' distances over specified periods of time. Use Bite-Sized Pieces and Process of Elimination to tackle this question. Begin by calculating the distance covered by a cheetah running for 15 min and a giraffe running for 5 min. Set up a proportion to determine the distance covered by a cheetah in 15 minutes, being sure to match up units: . Cross-multiply to get 10x = 270, then divide both sides by 10 to get x = 27 km. Repeat the process to determine the distance covered by a giraffe in 5 minutes: , which becomes 10x = 45, or x = 4.5 km. The total distance covered by a cheetah and a giraffe in the specified time periods is 27 km + 4.5 km = 31.5 km. Use a proportion to calculate the distance covered by each animal in each answer choice, and eliminate answer choices that are not close to this value. Choice (A) becomes , then 10x = 330, or x = 33 km. Keep (A) for now, as it is very close to the target value of 31.5, but check the remaining answer choices to see if one is closer. Choice (B) becomes , then 10x = 240, or x = 24 km. Eliminate (B), as it is not closer to 31.5 km than (A). Choice (C) becomes , then 10x = 700 km, or x = 70 km. Eliminate (C). Choice (D) becomes , then 10x = 420 km, or x = 42 km. Eliminate (D). The correct answer is (A).

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