In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs in a row. How many chairs are in the row?
(1) There is a total of 72 chairs.
(2) After one chair is removed from the last row, there is a total of 17 chairs in the last two rows.
OA is D
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Conference Room
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ronniecoleman
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1: N*(N-1) = 72
N = -8 , 9
N cannot be negative hence n = 9
2.
ADD 1 to 17 = 18
each row will have 18/2 = 9
hence we have 9 chairs
IMO D
N = -8 , 9
N cannot be negative hence n = 9
2.
ADD 1 to 17 = 18
each row will have 18/2 = 9
hence we have 9 chairs
IMO D
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cramya
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let the rows be R
let the chairs in each row be ch
r = ch-1
Stmt I
ch * (ch-1) = 72
Possible value ch = 9 ch-1 = 8
9 chairs
SUFF
Stmt II
one chair removed makes it 17 so there were 18 chair in2 rows before removing the 1 chair
Again 9 chairs
SUFF
D)
let the chairs in each row be ch
r = ch-1
Stmt I
ch * (ch-1) = 72
Possible value ch = 9 ch-1 = 8
9 chairs
SUFF
Stmt II
one chair removed makes it 17 so there were 18 chair in2 rows before removing the 1 chair
Again 9 chairs
SUFF
D)
Last edited by cramya on Sat Dec 13, 2008 9:43 pm, edited 1 time in total.
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sudhir3127
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i think this is a gmat prep question and the OA has to be D . Please make sure and doubly chk the questions and Answers before u post, It unncessarily creates confusion and takes a lot of time .Abdulla wrote:In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs in a row. How many chairs are in the row?
(1) There is a total of 72 chairs.
(2) After one chair is removed from the last row, there is a total of 17 chairs in the last two rows.
OA is C
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Abdulla
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I'm so sorry.. it was my mistake .. i didn't mean it.sudhir3127 wrote:i think this is a gmat prep question and the OA has to be D . Please make sure and doubly chk the questions and Answers before u post, It unncessarily creates confusion and takes a lot of time .Abdulla wrote:In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs in a row. How many chairs are in the row?
(1) There is a total of 72 chairs.
(2) After one chair is removed from the last row, there is a total of 17 chairs in the last two rows.
OA is C
Abdulla
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vittalgmat
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Yep got it .
I used one my take aways to reduce calculation and here it is.
(I am not sure if I can apply in all cases. So pls review and let me
know your feedback.)
Let the number of rows be r
stmt 1: says
r(r+1) = 72.
=> r^2 +r -72 = 0
72 is not a perfect square. So the two roots will be of opposite sign.
Dont care what it is. one of them is +ve which is what I need coz the
chairs and/or rows cannot be -ve. Therefore sufficient.
As a side note: I wonder if I can make the above conclusion.. what if the two roots are -ve something and a +ve fraction. Then both are invalid coz we cannot have fractional rows or chairs.
Am I taking a risk on the GMAT question by assuming that one of the roots will always be 'practical'??
Some one pls comment.
I used one my take aways to reduce calculation and here it is.
(I am not sure if I can apply in all cases. So pls review and let me
know your feedback.)
Let the number of rows be r
stmt 1: says
r(r+1) = 72.
=> r^2 +r -72 = 0
72 is not a perfect square. So the two roots will be of opposite sign.
Dont care what it is. one of them is +ve which is what I need coz the
chairs and/or rows cannot be -ve. Therefore sufficient.
As a side note: I wonder if I can make the above conclusion.. what if the two roots are -ve something and a +ve fraction. Then both are invalid coz we cannot have fractional rows or chairs.
Am I taking a risk on the GMAT question by assuming that one of the roots will always be 'practical'??
Some one pls comment.
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cramya
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Hard to tell.Am I taking a risk on the GMAT question by assuming that one of the roots will always be 'practical'??
Lets say eqn is x^2+6x+6 (6 is not a perfect square)
One distinct root but -ve.
IMO I would spend the extra 30 secs - minute to make sure it leads to the desired root to predict sufficiency.
Strictly my opinion.Hope I dint miss something in your logic above.
Regards,
Cramya
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pbanavara
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Honestly I wouldn't risk it .. when u r at this stage - it will take another 10 seconds to figure out the roots and the answer. May be 15 but I would spend the 15 secs and be sure of my answer.vittalgmat wrote:Yep got it .
I used one my take aways to reduce calculation and here it is.
(I am not sure if I can apply in all cases. So pls review and let me
know your feedback.)
Let the number of rows be r
stmt 1: says
r(r+1) = 72.
=> r^2 +r -72 = 0
72 is not a perfect square. So the two roots will be of opposite sign.
Dont care what it is. one of them is +ve which is what I need coz the
chairs and/or rows cannot be -ve. Therefore sufficient.
As a side note: I wonder if I can make the above conclusion.. what if the two roots are -ve something and a +ve fraction. Then both are invalid coz we cannot have fractional rows or chairs.
Am I taking a risk on the GMAT question by assuming that one of the roots will always be 'practical'??
Some one pls comment.
- pradeep
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vittalgmat
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vishubn
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Abdulla wrote:sudhir3127 wrote:i think this is a gmat prep question and the OA has to be D . Please make sure and doubly chk the questions and Answers before u post, It unncessarily creates confusion and takes a lot of time .Abdulla wrote:In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs in a row. How many chairs are in the row?
(1) There is a total of 72 chairs.
(2) After one chair is removed from the last row, there is a total of 17 chairs in the last two rows.
OA is C
In a way its FUN
One will not prove to get to the OA rather prove it to be right
Vishu
I'm so sorry.. it was my mistake .. i didn't mean it.
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