CBSE Class 10 Answered

R - Initial number of rows, S - Initial number of seats per row.

RS - Initial total number of seats.

As we do 2R, we get S-10, and total number of seats also increase,

(2R)(S-10) = RS + 300

2RS - 20R = RS + 300

But R = S  ..........Number of rows was equal to the number of seats in each row.

2R² - 20R = R² + 300

R² - 20R - 300 = 0

R = [20±(400+1200)]/2 = 30 and -10.

(1) The number of rows in original arrangement were, 30.

(2) The number of seats after the rearrangment were, (30)(30) + 300 = 1200.

Regards,

Team,

TopperLearning.