An auditorium has 15 rows with 20 seats in the front row, and 2 more seats in each row thereafter. How many seats are there in the last row?

Question

An auditorium has 15 rows with 20 seats in the front row, and 2 more seats in each row thereafter. How many seats are there in the last row?

Answer 1

Seats per row: 20, 22, 24, ...48 (last row is # 15); formula is 20 + 2(n-1) for # of seats in row n, n running from 1 to 15.