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GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2508
Given Kudos: 1053
GPA: 3.39
If one student is chosen randomly out of a group of seven st
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17 Mar 2020, 00:44
17 Mar 2020, 00:44
1
Expert Reply
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Question Stats:
57% (01:01) correct
42% (01:21) wrong based on 33 sessions
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If one student is chosen randomly out of a group of seven students, then one student is again chosen randomly from the same group of seven, what is the probability that two different students will be chosen?
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If one student is chosen randomly out of a group of seven st
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18 Mar 2020, 05:27
18 Mar 2020, 05:27
1
GeminiHeat wrote:
If one student is chosen randomly out of a group of seven students, then one student is again chosen randomly from the same group of seven, what is the probability that two different students will be chosen?
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
P(different student chosen each time) = P(ANY student chosen on 1st pick AND different student chosen on 2nd pick)
= P(ANY student chosen on 1st pick) x P(different student chosen on 2nd pick)
= 1 x 6/7
= 6/7
Answer: B
Cheers,
Brent
Re: If one student is chosen randomly out of a group of seven st
[#permalink]
01 May 2020, 00:58
01 May 2020, 00:58
GeminiHeat wrote:
If one student is chosen randomly out of a group of seven students, then one student is again chosen randomly from the same group of seven, what is the probability that two different students will be chosen?
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
(A) 36/49
(B) 6/7
(C) 19/21
(D) 13/14
(E) 48/49
Not a fan of this question. Choosing the first student is always 1/7, right? Ok. So then this is a "with replacement" question because you're picking again from the same set of 7. A different student from the first one chosen would be 6 out of 7, right? yes. So why isn't the answer 1/7 X 6/7 = 6/49. Makes no sense. Fortunately, because I don't see the answer, I would have guessed 6/7 anyway because that was part of my solution. Don't like this question at all (the source is "others,please specify," so it figures)
