# Help with summation

• October 5th 2009, 09:28 AM
coatesdr
Help with summation
Hi, I need some help with summation, I'm missing it in class today because I'm sick. The question I'm working on is:

Evaluate $\sum\left(\begin{array}{cc}n\\i\end{array}\right)* \frac{1}{2^n}$.

If $\sum\left(\begin{array}{cc}n\\i\end{array}\right)= 2^n$

would that mean $\sum\left(\begin{array}{cc}n\\i\end{array}\right)* \frac{1}{2^n}=\sum 1=n$?
• October 6th 2009, 11:30 AM
tonio
Quote:

Originally Posted by coatesdr
Hi, I need some help with summation, I'm missing it in class today because I'm sick. The question I'm working on is:

Evaluate $\sum\left(\begin{array}{cc}n\\i\end{array}\right)* \frac{1}{2^n}$.

If $\sum\left(\begin{array}{cc}n\\i\end{array}\right)= 2^n$

would that mean $\sum\left(\begin{array}{cc}n\\i\end{array}\right)* \frac{1}{2^n}=\sum 1=n$?

Correct

Tonio