SUM OF AP 1

The first term of an AP is 5 and the last term is 67. If the arithmetic progression consists of 20 terms, calculate the sum of all the terms. 

Solution

A₁ = 5, n=20, A_n = 67

S_n = n(A₁ + A_n)

       2

S₂₀ = 20(5 + 67)

         2

S₂₀ = 10 x 72

S₂₀ = 720

Hence the sum of all 20 terms is 720.

TRY THIS……………………….

The first term of an AP is 13 and the last term is 69. If the arithmetic progression consists of 16 terms, calculate the sum of all the terms.