Answered

Find the seating capacity of a movie house with 40 rows of seats if there are 25 seats in the first row, 28 seats in the second row, 31 seats in the third row and so on. f

Sagot :

Use Sum of the sequence formula:

Sn = n/2 [ 2(a₁) + (n-1)(d)]

n = 40

a₁ = 25

d = 3    ⇒  28-25 = 3

Substitute these values:

S₄₀ = 40/2 [2(25) + (40-1)(3)]

S₄₀ = 20 [50 + (39)(3)]

S₄₀ = 20 [50 + 117}

S₄₀ = 20 (167)

S₄₀ = 3,340

ANSWER: The seating capacity is 3,340.