Question

evaluate the sum of the finite geometric series.

Answer 1

\[\sum_{n=1}^{5} 3n\]

Answer 2

\[\sum_{n=1}^{5}3n=3+6+9+12+15\]

Answer 3

3+3=6
6+3=9
9+3=12 , etc.

It is a A.S.
Sum of A.S. =(1/2) (first term + last term)(no. of terms)
=(1/2)(3+15)(5) = 45