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a certain conference room

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a certain conference room

by sanju09 » Fri Apr 10, 2009 5:21 am
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 a row?

(1) There is a total of 72 chairs.

(2) After 1 chair is removed from the last row, there are a total of 17 chairs in the last 2 rows.



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by rs2010 » Sat Apr 11, 2009 4:13 am
stem says
Let x be row
y be column
x=y-1

1. x*y=72
2.2y-1=17

Ans D
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by bhumika.k.shah » Wed Feb 03, 2010 10:19 am
i still dint get it :(

Can someone please help me get an equation for the second statement ??
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by ajith » Wed Feb 03, 2010 10:27 am
sanju09 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 a row?

(1) There is a total of 72 chairs.

(2) After 1 chair is removed from the last row, there are a total of 17 chairs in the last 2 rows.



OA D
Say there are R no of rows with C no of chairs in each of them.

Now the number R is one less than the the number C

R = C-1

Total no of chairs = R*C

= (C-1)*C

1) (C-1)*C = 72 = 8*9

C=9 sufficient

2) 2*C -1 =17 [ each row has C seats, last row also had C seats, one was removed so C-1 seat, second last row has C seats, so total no of seats in last two rows = C-1+C = 2C-1]

C= 9 sufficient again

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D is the answer
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