Probability

swerve wrote: ↑

Wed Apr 15, 2020 3:05 pm

At a certain amateur bands rock show the ratio of freaks to nerds to geeks is 1 : 2 : 3. If these are the only types of people in the crowd, and each person in the crowd has the same chance of yelling "rock on!", what are the chances that the next person who yells "rock on!" will be a geek?

A. 1/6
B. 1/3
C. 1/2
D. 2/3
E. 5/6

The OA is C

Source: Economist GMAT

Given that the ratio of freaks to nerds to geeks is 1 : 2 : 3, say the no. of freaks = x, no. of nerds = 2x, and no. of geeks = 3x; thus, the total no. of people in the crowd = 6x

=> the chances that the next person who yells "rock on!" will be a geek = 3x/6x = 1/2

The correct answer: C

Hope this helps!

-Jay
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swerve wrote: ↑

Wed Apr 15, 2020 3:05 pm

At a certain amateur bands rock show the ratio of freaks to nerds to geeks is 1:2:3. If these are the only types of people in the crowd, and each person in the crowd has the same chance of yelling "rock on!", what are the chances that the next person who yells "rock on!" will be a geek?

A. 1/6
B. 1/3
C. 1/2
D. 2/3
E. 5/6

The OA is C

Source: Economist GMAT

The probability is 3/(1 + 2 + 3) = 3/6 = 1/2.

Answer: C