# Sum of series

by cgchayan
Tags: series
 P: 4 what will be the sum of this series? $$\Sigma$$ nCr . 2r where r = 0 to n
 P: 258 Hint: $$\sum_{r=0}^n _nC_r \cdot 2^r = \sum_{r=0}^n _nC_r \cdot 2^r \cdot 1^{n-r}$$