In the theatre, the number of seats in every row is four more than the number of seats of the preceding row. If there are 30 seats in the first row, what is the total seating capacity of the theatre if there are 30 rows?
+539 Row 1 has 30 seats, row 2 has 34, and so on.
The rule is Row x has 30+4(x-1) seats.
So row 30 would have 30+4(29) or 146 seats.
The sum of Row 1 and 30 is the same as the sum of rows 2 and 29, 3 and 28, and so on.
There are 15 pairs
146+30=176
176*15=2640.
