SUM OF A.P. 1

The first term of an AP is 41 and the last term is 107.If the arithmetic progression consists of 20 terms, calculate the sum of all the terms. 

Solution

A₁ = 41, n=20, A_n = 107

S_n = n(A₁ + A_n)

       2

S₂₀ = 20(41 + 107)

         2

S₂₀ = 10 x 148

S₂₀ = 1480

Hence the sum of all 20 terms is 1480.

TRYTHIS………………….

The first term of an AP is 15 and the last term is 113.If the arithmetic progression consists of 30 terms, calculate the sum of all the terms.