ARITHMETIC PROGRESSION 1

The first term of an AP is 41 and the last term is 97.If the arithmetic progression consists of 20 terms, calculate the sum of all the terms. 

Solution

A₁ = 41, n=20, A_n = 97

S_n = n(A₁ + A_n)

       2

S₂₀ = 20(41 + 97)

         2

S₂₀ = 10 x 138

S₂₀ = 1380

Hence the sum of all 20 terms is 1380.

TRYTHIS………………….

The first term of an AP is 11 and the last term is 53.If the arithmetic progression consists of 40 terms, calculate the sum of all the terms.