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

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In a class of 30 students, there are 17 girls and 13 boys. [#permalink] New post 24 Oct 2008, 14:16
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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.
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Re: Probability [#permalink] New post 24 Oct 2008, 14:27
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.
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Re: Probability [#permalink] New post 24 Oct 2008, 23:39
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
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Re: Probability [#permalink] New post 25 Oct 2008, 04:53
19/30.

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

Hence, probability = 19/30.
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Re: Probability [#permalink] New post 25 Oct 2008, 10:33
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
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Re: Probability [#permalink] New post 25 Oct 2008, 11:00
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] New post 25 Oct 2008, 12:42
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.
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Re: Probability [#permalink] New post 26 Oct 2008, 01:01
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] New post 27 Oct 2008, 10:07
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, 10:07
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