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What is the probability of selecting a white ball from a jar

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What is the probability of selecting a white ball from a jar

by Anaira Mitch » Sun Oct 22, 2017 3:58 am
What is the probability of selecting a white ball from a jar at random?

(1) There are twice as many white balls as balls of all other colors combined.
(2) There are 30 more white balls than balls of all other colors combined.

Source: VeritasPrep.
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Source: — Data Sufficiency |

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by Jay@ManhattanReview » Tue Oct 24, 2017 6:24 am
Anaira Mitch wrote:What is the probability of selecting a white ball from a jar at random?

(1) There are twice as many white balls as balls of all other colors combined.
(2) There are 30 more white balls than balls of all other colors combined.

Source: VeritasPrep.
(1) There are twice as many white balls as balls of all other colors combined.

Say # of balls of all other colors combined = y, thus, # of white balls = 2y

The probability of selecting a white ball from a jar = 2y/(y+2y) = 2/3. Sufficient.

(2) There are 30 more white balls than balls of all other colors combined.

Say # of balls of all other colors combined = y, thus, # of white balls = y + 30

The probability of selecting a white ball from a jar = (y + 30) / (y+30+y) = (y + 30) / (2y + 30). Inderminable value. Insufficient.

The correct answer: A

Hope this helps!

-Jay

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