A bag contains 5 red balls and some blue balls. If the probability of

Question

A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball is double that of a red ball, what the number of blue balls in the bag?

A. 8
B. 9
C. 10
D. 15
E. 20

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Abhishek009 · Answer

clearly (C), as probability of drawing blue balls is double only when no of blue balls is twice , only when no of blue balls is twice that of blue balls.

$!vakumar.m · Answer

A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball is double that of a red ball, what the number of blue balls in the bag?

Number of Red balls = 5
Number of blue balls = x

Probability of drawing a red ball = 5/(5+x)
Probability of drawing a blue ball = x/(5+x)
Given: x/(5+x) = 2*5/(5+x)
=> x = 10.
Answer C

ScottTargetTestPrep · Answer

We can let b = the number of blue balls.

The probability of drawing a red ball is 5/(5+b) and the probability of drawing a blue ball is b/5+b. Since the probability of drawing a blue ball is double that of a red ball, we have:

2 x 5/(5+b) = b/(5+b)

10/(5+b) = b/(5+b)

50 + 10b = 5b + b^2

b^2 - 5b - 50 = 0

(b - 10)(b + 5) = 0

b = 10

Answer: C

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GMAT Problem Solving (PS) Questions

A bag contains 5 red balls and some blue balls. If the probability of

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