In a certain conference room each row of chairs

[Guest-EG]

Hi- please help me in solving the below DS question from prep 1

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 is a total of 17 chairs in the last 2 rows.

[Sudhan]

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 is a total of 17 chairs in the last 2 rows.

Each Row= Equal Number of Chairs; #R = #C-1 What is C?

ADBCE Grid

1) Total C= 72; #R= 71; But it doesnt give enough info about the number of chairs in a row. Insuff
2) R(Last)= R(Last)-1; R(Last)+R(last-1)= 17; Based on this fact, we cannot determine how many chairs each row has? Insuff

Combining 1 and 2, # of Rows= 71 (Since #R= #c-1 where c= 72)
R70+R71= 17; After adding 1chair to R71 we get R70+R71=18; But it could be combination of 10+8; 9+9; 8+10.

Hence Insuff..

I think answer is E.

What is OA?

[Guest-EG]

actually the correct answer is d

[vikram]

let there be x chairs in each row, therefore there are x-1 rows. Total chairs in room x(x-1)

1) x(x-1)=72, x=9;suff

2) x+(x-1)=17,x=9;suff

Hence D

[Guest-EG]

Thanks Vikram!

[rfernandez]

Nice solution, Vikram!