SOLUTION: a theater has 36 rows with 21 seats in the first row, 24 in the second row, 27 in the tird row ans so forth. hOw many seats are in the theater?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: a theater has 36 rows with 21 seats in the first row, 24 in the second row, 27 in the tird row ans so forth. hOw many seats are in the theater?      Log On


   

Question 475683: a theater has 36 rows with 21 seats in the first row, 24 in the second row, 27 in the tird row ans so forth. hOw many seats are in the theater?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Sum of an arithmetic sequence is S%5Bn%5D+=+%28n%2F2%29%282a%5B1%5D+%2B+%28n-1%29d%29.
Here, a%5B1%5D+=+21, n = 36, and d = 3.
==> S%5B36%5D+=+%2836%2F2%29%282%2A21+%2B+35%2A3%29+=+18%2A147+=+2646 seats.