Use summation notation to write the sum. $0.9 + 3.6 + 14.4 + \ldots + 921.6$
A) $\sum _ { n = 1 } ^ { 8 } 0.9 ( 4 ) ^ { n + 1 }$
B) $\sum _ { n = 1 } ^ { 6 } ( 4 ) ^ { n - 1 }$
C) $\sum _ { n = 1 } ^ { 7 } 0.9 ( 4 ) ^ { n - 1 }$
D) $\sum _ { n = 1 } ^ { 8 } 0.9 ( 4 ) ^ { n }$
E) $\sum _ { n = 1 } ^ { 6 } 0.9 ( 4 ) ^ { n - 1 }$

Question

Use summation notation to write the sum.   $0.9 + 3.6 + 14.4 + \ldots + 921.6$  
A) $\sum _ { n = 1 } ^ { 8 } 0.9 ( 4 ) ^ { n + 1 }$
B) $\sum _ { n = 1 } ^ { 6 } ( 4 ) ^ { n - 1 }$
C) $\sum _ { n = 1 } ^ { 7 } 0.9 ( 4 ) ^ { n - 1 }$
D) $\sum _ { n = 1 } ^ { 8 } 0.9 ( 4 ) ^ { n }$
E) $\sum _ { n = 1 } ^ { 6 } 0.9 ( 4 ) ^ { n - 1 }$

Quizplus · Accepted Answer

The sequence is geometric with the first term 0.9 and a common ratio of 4. The nth term is given by $0.9 \times 4^{n-1}$. The last term is 921.6, which is the 6th term, so the sum is $\sum_{n=1}^{6} 0.9 (4)^{n-1}$.

Use Summation Notation to Write the Sum 0.9+3.6+14.4+…+921.60.9 + 3.6 + 14.4 + \ldots + 921.60.9+3.6+14.4+…+921.6

Use Summation Notation to Write the Sum $0.9 + 3.6 + 14.4 + \ldots + 921.6$