SOLUTION: An auditorium has 20 seats on the first row, 24 seats on the second row, 28 seats on the third row, and so on and has 30 rows of seats. How many seats are in the theatre?

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Question 864040: An auditorium has 20 seats on the first row, 24 seats on the second row, 28 seats on the third row, and so on and has 30 rows of seats. How many seats are in the theatre?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
S = ½(2a + (n-1)d)n
S = ½(2*20 + (29)4)30
S=15*(156)=2340