ARITHMETIC PROGRESSION 1

Find the sum of the 1st 16 terms of the following arithmetic progression: 5+11+17+…………………

Solution

d=6, A₁ = 5,n=16

S_n = n[2A₁ + (n-1)d]

       2

S₁₆ = 16[2(5) + (16-1)d]

         2

S₁₆ = 8[10 + 15d]

 

S₁₆ = 8[10 + 13(6)]       since d=6

S₁₆ = 8[10 + 78]  

         

S₁₆ = 8 x 88 

          

S₁₆ = 704

Therefore the sum of 1st 16 terms is 704.

TRY THIS............

Find the sum of the 1st 12 terms of the following arithmetic progression: 7+10+13+…………………