Question

The sum of first 16 terms of the AP 10, 6, 2, ….. is 

A. - 320  B. 320 C. - 352 D. - 400

Answer 1

A. -320

Given,

First term, a = 10

Common Difference, d = 6 - 10 = - 4(a₂ - a₁)

Using the formula,

Where S_n is the sum of first n terms

n = no of terms

a = first term

d = common difference

S₁₆ = (16/2)[ 2(10) + (16 - 1) (- 4)]

= 8(20 - 60)

= - 320