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In a class of 30 students, there are 17 girls and 13 boys.

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Director
Joined: 05 Jan 2008
Posts: 688
In a class of 30 students, there are 17 girls and 13 boys. [#permalink]

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28 Jun 2008, 01:06
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In a class of 30 students, there are 17 girls and 13 boys. Five are A students, and three of these students are girls. If a student is chosen at random, what is the probability of choosing a girl or an A student?
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Joined: 12 Apr 2008
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28 Jun 2008, 04:36
Quote:
In a class of 30 students, there are 17 girls and 13 boys. Five are A students, and three of these students are girls. If a student is chosen at random, what is the probability of choosing a girl or an A student?

I got 19/30:

If three of A students are girls => 2 are boys.
P = P(choose any girl) + P(choose boy who is A) = 17/30 + 2/30 = 19/30.
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Joined: 27 May 2008
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28 Jun 2008, 04:48
G : set of all girls = 17
A : set of all A students = 5
GiA : G intersection A = 3
GUA : G union A

P(GUA) = P(G) + P(A) - P(GiA)
= 17/30 + 5/30 - 3/30
=19/30
Re: PS: Probability   [#permalink] 28 Jun 2008, 04:48
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