Use summation notation to write each sum. Then evaluate the sum if it exists.

1. $5+15+$$25+\dots+215$ 

   Hint (a):

   This is an arithmetic series with a first term of $5$ and a common difference of $10$.
   How many terms are in the series? This information is needed to calculate the sum.

2. $2+\frac{1}{2}+$$\frac{1}{8}+\ldots+\frac{1}{512}$ 

   Hint (b):

   This is a geometric series with a first term of $2$ and a common ratio of $0.25$.
   How many terms are in the series? This information is needed to calculate the sum.

3. $3−4+$$\frac{16}{3}-\frac{64}{9}+\ldots$ 

   Hint (c):

   This is an infinite geometric series. What is the common ratio? How does this affect the sum?