ARITHMETIC PROGRESSION 1E

 

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 7 and the last term is 75. If the arithmetic progression consists of 24 terms, calculate the sum of all the terms