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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]

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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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Manager
Joined: 15 Oct 2008
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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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Director
Joined: 14 Aug 2007
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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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SVP
Joined: 17 Jun 2008
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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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VP
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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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VP
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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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Senior Manager
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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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VP
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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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"You have to find it. No one else can find it for you." - Bjorn Borg

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Manager
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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.

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Re: Probability   [#permalink] 27 Oct 2008, 10:07
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# In a class of 30 students, there are 17 girls and 13 boys.

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