Question

Large multiplex movie house has many theaters The largest theater has 40 rose they are 10 seats in the first row each row has four seats more than the previous row how many total seats are in the theater

Answer 1

There are total 3,520 seats in the theater.

Explanation:

Given that,

A theater has 40 rows and there are 10 seats in first row. Each row has four seats more than the previous row.

Row Number of seat

1 10

2 10+4=14

3 14+4=18

.....

The number of seat increase in A.P.

Sum of A.P series
`S_n=\frac n2\{2a+(n-1)d\}`

Here a= 10, d=4,n=40.

`S_(40)=\frac {40}2\{2.10+(40-1)4\}`

=20(20+39.4)

=3,520

Total number seats are 3,520 in the theater.