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

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Senior Manager
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In a class of 30 students, there are 17 girls and 13 boys. [#permalink]  24 Oct 2008, 13:16
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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?

A. 19/30
B. 11/15
C. 17/180
D. None of the above.
Manager
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Re: Probability [#permalink]  24 Oct 2008, 13:27
axl_oz wrote:
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?

A. 19/30
B. 11/15
C. 17/180
D. None of the above.

B.
The Probability of choosing a girl is 17/30.
The probability of choosing an A student is 5/30
The P(girl) + the P(A student) = 17/30 + 5/30 = 22/30 = 11/15.

Pls let me know if it is the correct answer.
Director
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Re: Probability [#permalink]  24 Oct 2008, 22:39
axl_oz wrote:
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?

A. 19/30
B. 11/15
C. 17/180
D. None of the above.

I think
17/30 + 2/30 = 19/30

2/30 is because 17/30 includes all the girls (including A girls)

I am not sure though
SVP
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Re: Probability [#permalink]  25 Oct 2008, 03:53
19/30.

Number that represents girls or A students = 17 + 2 = 19

Hence, probability = 19/30.
VP
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Re: Probability [#permalink]  25 Oct 2008, 09:33
P (girl or A students ) = P (girl) + p ( A student) - P ( girl and A student) Hence it is 17/30 + 5/30 - 3/30 = 19/30
VP
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Re: Probability [#permalink]  25 Oct 2008, 10:00
icandy wrote:
P (girl or A students ) = P (girl) + p ( A student) - P ( girl and A student) Hence it is 17/30 + 5/30 - 3/30 = 19/30

why do we do - P ( girl and A student) ?
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Re: Probability [#permalink]  25 Oct 2008, 11:42
amitdgr wrote:
icandy wrote:
P (girl or A students ) = P (girl) + p ( A student) - P ( girl and A student) Hence it is 17/30 + 5/30 - 3/30 = 19/30

why do we do - P ( girl and A student) ?

17 includes the 3 girls in A , so we need to find out the probability of A sans girls since the girls have already been counted in 17.
VP
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Re: Probability [#permalink]  26 Oct 2008, 00:01
Nihit wrote:
amitdgr wrote:
icandy wrote:
P (girl or A students ) = P (girl) + p ( A student) - P ( girl and A student) Hence it is 17/30 + 5/30 - 3/30 = 19/30

why do we do - P ( girl and A student) ?

17 includes the 3 girls in A , so we need to find out the probability of A sans girls since the girls have already been counted in 17.

Ahh !! I get it now

thanks
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Re: Probability [#permalink]  27 Oct 2008, 09:07
icandy wrote:
P (girl or A students ) = P (girl) + p ( A student) - P ( girl and A student) Hence it is 17/30 + 5/30 - 3/30 = 19/30

Thanks, icandy. I think you are right.
Re: Probability   [#permalink] 27 Oct 2008, 09:07
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