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A certain business school has 500 students, and the law school at the
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22 Oct 2021, 06:55
22 Oct 2021, 06:55
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A certain business school has 500 students, and the law school at the same university has 800 students. Among these students, there are 30 sibling pairs consisting of 1 business student and 1 law student. If 1 student is selected at random from both schools, what is the probability that a sibling pair is selected?
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
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Re: A certain business school has 500 students, and the law school at the
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22 Oct 2021, 07:16
22 Oct 2021, 07:16
Carcass wrote:
A certain business school has 500 students, and the law school at the same university has 800 students. Among these students, there are 30 sibling pairs consisting of 1 business student and 1 law student. If 1 student is selected at random from both schools, what is the probability that a sibling pair is selected?
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
P(selecting a sibling pair) = P(select a business student with a sibling AND select a law student who is that business student's sibling)
= P(select a business student with a sibling) x P(select a law student who is that business student's sibling)
= 30/500 x 1/800
= 30/400,000
= 3/40,000
Answer: A
Note: P(select a business student with a sibling) = 30/500, because 30 of the 500 business students have a sibling in law school.
P(select a law student who is that business student's sibling) = 1/800, because there are 800 law students and only 1 is the sibling of the selected business student.
Cheers,
Brent
Re: A certain business school has 500 students, and the law school at the
[#permalink]
29 Jul 2023, 05:29
29 Jul 2023, 05:29
You counted: (30/500)*(1/800)
But what about: (30/800)*(1/500)?
(30/500)*(1/800) + (30/800)*(1/500) = 60/400000 = 3/20000
Answer: B
Why is it wrong?
P(selecting a sibling pair) = P(select a business student with a sibling AND select a law student who is that business student's sibling)
= P(select a business student with a sibling) x P(select a law student who is that business student's sibling)
= 30/500 x 1/800
= 30/400,000
= 3/40,000
Answer: A
Note: P(select a business student with a sibling) = 30/500, because 30 of the 500 business students have a sibling in law school.
P(select a law student who is that business student's sibling) = 1/800, because there are 800 law students and only 1 is the sibling of the selected business student.
Cheers,
Brent
But what about: (30/800)*(1/500)?
(30/500)*(1/800) + (30/800)*(1/500) = 60/400000 = 3/20000
Answer: B
Why is it wrong?
GreenlightTestPrep wrote:
Carcass wrote:
A certain business school has 500 students, and the law school at the same university has 800 students. Among these students, there are 30 sibling pairs consisting of 1 business student and 1 law student. If 1 student is selected at random from both schools, what is the probability that a sibling pair is selected?
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
A. \(\frac{3}{40000}\)
B. \(\frac{3}{20000}\)
C. \(\frac{3}{4000}\)
D. \(\frac{9}{400}\)
E. \(\frac{6}{130}\)
P(selecting a sibling pair) = P(select a business student with a sibling AND select a law student who is that business student's sibling)
= P(select a business student with a sibling) x P(select a law student who is that business student's sibling)
= 30/500 x 1/800
= 30/400,000
= 3/40,000
Answer: A
Note: P(select a business student with a sibling) = 30/500, because 30 of the 500 business students have a sibling in law school.
P(select a law student who is that business student's sibling) = 1/800, because there are 800 law students and only 1 is the sibling of the selected business student.
Cheers,
Brent
