## College Algebra (6th Edition)

Number of seats in first Row = 30 Number of seats increase per Row = 2 By formula $a_{n}$ = $a_{1}$ + (n-1)d Number of seats in $26^{th}$ Row = 30 + (26 - 1)$\times$2 = 30 + 50 = 80 By formula The sum $S_{n}$ = $\frac{n}{2}$(first term + last term) Total number of seats in theater = $\frac{26}{2}$( 30 + 80) = 13$\times$110 = 1430