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There are n students in a class. Of them, k boys and k girls (includin
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29 Jan 2015, 07:25
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There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
Re: There are n students in a class. Of them, k boys and k girls (includin
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09 Feb 2015, 06:39
4
1
pacifist85 wrote:
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
I agree with A and the explanations.
What I would like to ask refers to the part in red. If we have 6 boys and 6 girls that will be paired together, don't we have 6*6=36 combinations of possibl pairs? So, 36 possible, different pairs? Out of these 36 pairs, Harvey and Jessica together would make one pair. So, isn't the probability 1/36?
hi pacifist, selection of harvey is already sure as he is one of the k boys selected.. And he can be paired with any of the 6(k) girls... so it will be 1/6..
1/36 would have been correct in following scenarios.. 1) there are 6 boys and 6 girls. Out of these one boy and one girl are to be choosen as a pair for dance. what is the prob of choosing harvey and jessica? 2) there are 6 boys, harvey being one of them. these 6 boys are to be paired with one of 36 girls, jessica being one of them.what is the prob of harvey being paired with jessica?
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Re: There are n students in a class. Of them, k boys and k girls (includin
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29 Jan 2015, 10:09
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Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
Kudos for a correct solution.
ans A.. 1) statement tells us k=6. sufficient 2) statement 2 not clear as k boys are selected how can 8 out of them not selected... it must be n and not k...insufficient
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Re: There are n students in a class. Of them, k boys and k girls (includin
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29 Jan 2015, 10:33
chetan2u wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
Kudos for a correct solution.
ans A.. 1) statement tells us k=6. sufficient 2) statement 2 not clear as k boys are selected how can 8 out of them not selected... it must be n and not k...insufficient
chetan2u, would you mind explaining how do you get that the answer is A? Statement (1) just gives us k, but we still don't know n... Or k is enough information to tell that the probability of Harvey paired with Jessica is 1/6?
Re: There are n students in a class. Of them, k boys and k girls (includin
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29 Jan 2015, 10:38
viktorija wrote:
chetan2u wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
Kudos for a correct solution.
ans A.. 1) statement tells us k=6. sufficient 2) statement 2 not clear as k boys are selected how can 8 out of them not selected... it must be n and not k...insufficient
chetan2u, would you mind explaining how do you get that the answer is A? Statement (1) just gives us k, but we still don't know n... Or k is enough information to tell that the probability of Harvey paired with Jessica is 1/6?
hi victorija.... as k boys and girls are already selected so k in itself becomes a certainity and n does not have any role in calculating probability..
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Re: There are n students in a class. Of them, k boys and k girls (includin
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01 Feb 2015, 14:23
1
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
Kudos for a correct solution.
Statement 1: Harvey plus 5 boys = K. So K is 6...so there are six boys and six girls...can calculate probability of one particular pairing. Sufficient.
Statement 2: Unclear. Question states K boys and K girls are selected for the dance...this statement says 8 of those K boys are not selected. Doesn't make any sense to me.
Going with A.
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Re: There are n students in a class. Of them, k boys and k girls (includin
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02 Feb 2015, 02:40
1
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Re: There are n students in a class. Of them, k boys and k girls (includin
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04 Feb 2015, 10:49
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
I think veritas made a mistake. Number (2) clearly should be 8 of the n boys.
Re: There are n students in a class. Of them, k boys and k girls (includin
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09 Feb 2015, 06:28
1
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
I agree with A and the explanations.
What I would like to ask refers to the part in red. If we have 6 boys and 6 girls that will be paired together, don't we have 6*6=36 combinations of possibl pairs? So, 36 possible, different pairs? Out of these 36 pairs, Harvey and Jessica together would make one pair. So, isn't the probability 1/36?
Re: There are n students in a class. Of them, k boys and k girls (includin
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09 Feb 2015, 06:48
Oh great chetan2u, thank you very much. I actually thought we were talking about the first of the 2 possibilities you provided as an example of a 1/36 probability. Kudos for your help.
Re: There are n students in a class. Of them, k boys and k girls (includin
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17 Nov 2016, 09:52
Hi,
I have one doubt in the question. Option A mentions that Harvey is selected, and we can correctly conclude that there are 6 boys and 6 girls selected. But how can we come to the conclusion that Jessica is among these 6 girls. Am I on a wrong track here?
Re: There are n students in a class. Of them, k boys and k girls (includin
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03 Dec 2016, 03:28
AnkurBansal89 wrote:
Hi,
I have one doubt in the question. Option A mentions that Harvey is selected, and we can correctly conclude that there are 6 boys and 6 girls selected. But how can we come to the conclusion that Jessica is among these 6 girls. Am I on a wrong track here?
Regards,
Ankur
Dear Ankur,
We are being told that there are K girls and K boys including Jessica and Harvey out of which we need to select pair for dance performance (one girl can be paired with one boy). Now, statement 1 tells us that a total of 6 boys are selected (including Harvey). Now, this tells us that the total number of girls is also 6 as the question stem tells us that equal number of girls and boys are selected (k) and stem also tells us that Harvey is one of those 6 girls (the question stem tells us that there are K girls and boys including Harvey and Jessica. This means that both of them are included in k). Does that help ?
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Re: There are n students in a class. Of them, k boys and k girls (includin
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21 Mar 2017, 00:24
Statement 2 is not well phrased. I lost time trying to understand what was meant. Cheers.
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Re: There are n students in a class. Of them, k boys and k girls (includin
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28 Apr 2017, 15:37
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
Bunuel I could not understand why we need total number of boys - k?
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Re: There are n students in a class. Of them, k boys and k girls (includin
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29 Apr 2017, 02:51
ziyuen wrote:
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
Bunuel I could not understand why we need total number of boys - k?
What do you mean why we need this? This is what the second statement is saying. It's not sufficient but it is what it is telling us.
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Re: There are n students in a class. Of them, k boys and k girls (includin
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23 Sep 2017, 13:19
Top Contributor
Bunuel wrote:
Bunuel wrote:
There are n students in a class. Of them, k boys and k girls (including Harvey and Jessica) are selected for a dance performance in which students will dance in pairs of one boy and one girl. What is the probability that Harvey will be paired with Jessica?
(1) Other than Harvey, 5 boys are selected for the dance.
(2) 8 of the k boys are not selected for the dance.
There are k boys and k girls selected (including Harvey and Jessica). Harvey can be paired with any one of the k girls. Jessica is one of the girls. The probability that Harvey will be paired with Jessica is 1/k. Notice that n has no role to play here. The required probability only needs the value of k.
Statement 1: We now know that total 5+1 = 6 boys and 6 girls were selected for the dance. So probability that Harvey will be paired with Jessica is 1/6. Sufficient.
Statement 2: This tells us that Total number of boys – k = 8. We don’t know the value of k. Not sufficient.
Answer (A)
I think there's an issue with statement 2.
On the GMAT, the two statements in a Data Sufficiency (DS) question will never contradict each other. For example, the following question would never be a legitimate DS question:
What is the value of x" (1) x + 1 = 5 (2) 2x = 6
Here, statement 1 tells us that x = 4, and statement 2 tells us that x = 3 As such, this question does not adhere to the format of official DS questions.
In the original question, we learned (from statement 1) that k = 6 So, statement 2 is basically telling us that "8 of the 6 boys are not selected for the dance," and this contradicts the information provided in statement 1.
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