SUM OF AP K1

The first term of an AP is 13 and the last term is 57.If the arithmetic progression consists of 40 terms, calculate the sum of all the terms. 

 

Solution

 

A₁ = 13, n=40, A_n= 57

 

Sn = n(A₁ + A_n)

      2

 

S₂₀ = 40(13 + 57)

       2

 

S₂₀ = 20 x 70

 

S₂₀ = 1400

 

 Hence the sum of all 20 terms is 1400.

 

TRY THIS………….

 

The first term of an AP is 11 and the last term is 163.If the arithmetic progression consists of 60 terms, calculate the sum of all the terms.