SAT Math Multiple Choice Practice Question 284: Answer and Explanation

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Question: 284

20. In a class of 160 seniors, the ratio of boys to girls is 3 to 5. In the junior class, the ratio of boys to girls is 3 to 2. When the two classes are combined, the ratio of boys to girls is 1 to 1. How many students are in the junior class?

A. 400
B. 360
C. 200
D. 180
E. 160

Correct Answer: C

Explanation:

C If the ratio of boys to girls in a class is 3 to 5, then of the class is boys and of the class is girls. This means there are boys and girls in the senior class. Similarly, the fraction of boys in the junior class is and the fraction of girls is . If there are x students in the junior class, then there are () x boys and () x girls in the junior class. If the ratio of boys to girls is 1:1 when the classes are combined, then

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