Question

The sum of 25 terms of A.P. 8 + 12 + 16 + .... is ______.

विकल्प

• 1400

• 1600

• 1800

• 2000

Answer 1

The sum of 25 terms of A.P. 8 + 12 + 16 + .... is 1400.

Explanation:

a =  8

d = 12 − 8

= 4

n = 25

`S_n = n/2[2a + (n - 1)d]`

`S_25 = 25/2[2(8) + (25 - 1)4]`

`S_25 = 25/2[16 + (24)4]`

`S_25 = 25/2[16 + 96]`

`S_25 = 25/2[112]`

S₂₅ = 25 × 56

S₂₅ = 1400