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

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Bunuel
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In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   13 Nov 2018, 10:44
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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. 17/180
B. 19/30
C. 11/15
D. 14/15
E. None of the above.
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   27 Jan 2019, 19:42
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Bunuel 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. 17/180
B. 19/30
C. 11/15
D. 14/15
E. None of the above.


The probability of choosing a girl or an A student is:

P(girl or A) = P(girl) + P(A) - P(both girl and A)

17/30 + 5/30 - 3/30 = 19/30

Answer: B
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   14 Nov 2018, 02:17
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Bunuel 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. 17/180
B. 19/30
C. 11/15
D. 14/15
E. None of the above.


Good question:

P of Girl= 17/30
P of a student= 5/30
and since we are double counting girls so we need to minus A girl students= 3/30

(17/30)+(5/30)-(3/30)
=19/30 option B
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   13 Nov 2018, 10:52
Probability of choosing girl = 17/30
Probability of choosing an A student = 5/30

So, probability of choosing a girl or an A student = (17/30) + (5/30) = 22/30 = 11/15

Option C
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   13 Nov 2018, 17:52
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I thought it would be B because we need to minus 3/30 probably that's both girl and A student
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   13 Nov 2018, 18:20
Lilmermaid wrote:
I thought it would be B because we need to minus 3/30 probably that's both girl and A student


I think you are right. My bad. Picking a girl and picking an A student are not mutually exclusive events and hence 3/30 should be subtracted! Thanks!

This goes into the error log!
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Re: In a class of 30 students, there are 17 girls and 13 boys. Five are A [#permalink] New post   14 Apr 2024, 03:51
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