ARITHMETIC PROGRESSION 5

The first term of an AP is 13 and the last term is 57.If the arithmetic progression consists of 20 terms, calculate the sum of all the terms. 

Solution

A₁ = 13, n=20, A_n = 57

S_n = n(A₁ + A_n)

      2

S₂₀ = 20(13 + 57)

        2

S₂₀ = 10 x 70

S₂₀ = 700

Hence the sum of all 20 terms is 700.

TRY THIS………….

The first term of an AP is 11 and the last term is 63.If the arithmetic progression consists of 30 terms, calculate the sum of all the terms.