Question

A theater has 30 seats in the first row, 33 seats in the second row, 36 seats in the third row, and so on in the same increasing pattern. If the theater has 15 rows of seats, how many seats are in the theater?

Answer 1

Keep on adding...

30+33+36+39+42+45+48+51+54+57+60+63+66+69+72

Which equals up to 765 seats

Answer 2

Number of seats in theater=765

Explanation:

A theater has 30 seats in the first row

33 seats in the second row

36 seats in the third row

and so on

the pattern of seats will be

30 33 36 39 42 45 48 51 54 57 60 63 66 69 72

The upper pattern is in arithmetic progression having n=15 terms

sum of arithmetic progression is

n(first term+last term)/2

hence, number of seats in theater= 15(30+72)/2

= 765