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separate generic traits

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separate generic traits

by sanju09 » Thu Mar 19, 2009 6:28 am
Let A, B and C denotes separate generic traits. Suppose the probability that an individual will exhibit trait A is 1/2 and the probability that he exhibits B trait is 3/4 and the probability that he exhibits trait C is 3/5. What is the probability that he exhibits only one of the traits?

A. 1/4
B. 11/40
C. 1/6
D. 17/36
E. 11/36


OA B
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by hijazim » Thu Mar 19, 2009 7:20 am
The correct answer is B.
The probability that any person will only have one of the traits and any of the other two is:

P(A, not B, not C) or P(not A, B, Not C) or P(not A, not B, C)
= 1/2 x 1/4 x 2/5 + 1/2 x 3/4 x 2/5 + 1/2 x 1/4 x 3/5 = 11/40

Hence, answer B.
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by sureshbala » Thu Mar 19, 2009 7:27 am
Probability that he exhibits only trait A = 1/2 x 1/4 x 2/5= 2/40
Probability that he exhibits only trait B = 1/2 x 3/4 x 2/5= 6/40
Probability that he exhibits only trait C = 1/2 x 1/4 x 3/5= 3/40

Hence total probability = 2/40+6/40+3/40 = 11/40.

Am i missing something here?
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