Question

There are six friends of Saurav. In how many ways he can invite one or more friends to take dinner?

Answer 1

Number of ways $={}^6{C}_1+{}^6{C}_2+{}^6{C}_3+{}^6{C}_4+{}^6{C}_5$

$=6+\frac{6\times 5}{2}+\frac{6\times 5\times 4}{3\times 2}+\frac{6\times 5}{2}+6+1$

$=6+15+20+15+7$

$=63$