Question

Calculate the sum:

Answer 1

A 5.3333
B 42.6666
C 10.6666
D 21.3333

Answer 2

use that it is a geometric series to find the sum

Answer 3

\[\sum_{i=1}^{n}a \cdot r^i=a r\cdot \frac{1-r^n}{1-r} \\\]
you have
\[(\sum_{i=1}^{n}ar^i)-ar^1\]