Question

A classroom has stadium. There are 10 seats in the first row, 13 seats in the second row, 16 seats in the third row and so on. There are 56 rows what is the seating capacity of the class?

The classroom has 4,900 seats.

The classroom has 5,180 seats.

The classroom has 4,995 seats

The classroom has 5,348 seats​

Answer 1

B

5180

Explanation:

a1 = 10

n = 56

d = 3

L = a1 + (n - 1)*d

L = 10 + 55*3

L = 10 + 165

L = 175

Sum = (a1 + L)*n/2

Sum = (10 + 175)*56/2

Sum = 185 * 56/2

Sum = 185 * 28

Sum = 5180

The answer is B