Find the sum of the infinite series. $\sum _ { i = 1 } ^ { \infty } 4 \left( \frac { 1 } { 10 } \right) ^ { i }$
A) $\frac { 4 i } { 9 }$
B) $\frac { 4 } { 9 }$
C) $\frac { 9 i } { 4 }$
D) $- \frac { 4 i } { 9 }$
E) $\frac { 9 } { 4 }$

Question

Find the sum of the infinite series.   $\sum _ { i = 1 } ^ { \infty } 4 \left( \frac { 1 } { 10 } \right) ^ { i }$  
A) $\frac { 4 i } { 9 }$
B) $\frac { 4 } { 9 }$
C) $\frac { 9 i } { 4 }$
D) $- \frac { 4 i } { 9 }$
E) $\frac { 9 } { 4 }$

Quizplus · Accepted Answer

This is a geometric series with the first term $a = 4 \times \frac{1}{10} = \frac{4}{10}$ and common ratio $r = \frac{1}{10}$. The sum of an infinite geometric series is given by $S = \frac{a}{1 - r}$, where $|r| < 1$. Substituting $a = \frac{4}{10}$ and $r = \frac{1}{10}$ gives $S = \frac{\frac{4}{10}}{1 - \frac{1}{10}} = \frac{\frac{4}{10}}{\frac{9}{10}} = \frac{4}{9}$.

Find the Sum of the Infinite Series ∑i=1∞4(110)i\sum _ { i = 1 } ^ { \infty } 4 \left( \frac { 1 } { 10 } \right) ^ { i }∑i=1∞​4(101​)i

Find the Sum of the Infinite Series $\sum _ { i = 1 } ^ { \infty } 4 \left( \frac { 1 } { 10 } \right) ^ { i }$