In a theatre, there are 20 seats in the front row and 30 rows were all

1.	In a theatre, there are 20 seats in the front row and 30 rows were allotted. Each successive row contains two additional seats than its front row. How many seats are there in the last row?
Answer» Number of seats in the first row (a) = 20 ∴ t₁ = 20 Number of seats in the second row (t₂) = 20 + 2 = 22 Number of seats in the third row (t₃) = 22 + 2 = 24 Here a = 20 ; d = 2 Number of rows (n) = 30 t_n = a + (n – 1)d t₃₀= 20 + 29(2) = 20 + 58 t₃₀ = 78 Number of seats in the last row is 78

In a theatre, there are 20 seats in the front row and 30 rows were allotted. Each successive row contains two additional seats than its front row. How many seats are there in the last row?

Answer»

Number of seats in the first row

(a) = 20

∴ t₁ = 20

Number of seats in the second row

(t₂) = 20 + 2 = 22

Number of seats in the third row

(t₃) = 22 + 2 = 24

Here a = 20 ; d = 2

Number of rows

(n) = 30

t_n = a + (n – 1)d

t₃₀= 20 + 29(2)

= 20 + 58

t₃₀ = 78

Number of seats in the last row is 78