Q16 of 89 Page 45

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

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

The famous mathematician associated with finding the sum of the first 100 natural numbers is

If the first term of an AP is - 5 and the common difference is 2, then the sum of the first 6 terms is

In an AP, if a = 1, a_n = 20 and S_n = 399, then n is equal to

The sum of first five multiples of 3 is