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In a group of 800 people, 1/5 play at least one instrument..

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In a group of 800 people, 1/5 play at least one instrument.. [#permalink] New post 05 Aug 2012, 07:00
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C
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In a group of 800 people, 1/5 play at least one instrument, 96 play two or more. What is the probability that one student play exactly one instrument?

A) 2/125
B) 3/125
C)2/25
D) 3/25
E) 1/5
[Reveal] Spoiler: OA

Last edited by ferrarih on 05 Aug 2012, 15:58, edited 2 times in total.
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Re: In a group with 800 people... [#permalink] New post 05 Aug 2012, 07:08
Expert's post
ferrarih wrote:
In a grouup of 800 people, 1/5 play at least one instrument, 96 play two or more. Whats it is e probability that one student play exactly one instrument?

A) 2/125
B) 3/125
C)2/25
D) 3/25
E) 1/5


Given that 1/5*800=160 students play 1 or more instrument and 96 play 2 or more, so 160-96=64 students play exactly 1 instrument.

Therefore the probability that a randomly chosen student plays exactly one instrument is 64/800=2/25.

Answer: C.
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Re: In a group with 800 people... [#permalink] New post 05 Aug 2012, 07:14
ferrarih wrote:
In a grouup of 800 people, 1/5 play at least one instrument, 96 play two or more. Whats it is e probability that one student play exactly one instrument?

A) 2/125
B) 3/125
C)2/25
D) 3/25
E) 1/5


P(playing 2 or more instruments) = 96/800 = 3/25.
Then, the probability of playing exactly one instrument is given by:
P(playing 1 or more instruments) - P(playing 2 or more instruments) = 1/5 - 3/25 = 2/25.

Answer C.
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Re: In a group of 800 people, 1/5 play at least one instrument.. [#permalink] New post 13 Jul 2013, 23:11
Expert's post
Re: In a group of 800 people, 1/5 play at least one instrument..   [#permalink] 13 Jul 2013, 23:11
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