0 votes 0 votes Give a combinatorial proof that $\displaystyle{}\sum_{k = 1}^{n} k \binom{n}{k} = n2^{n−1}.$ [Hint: Count in two ways the number of ways to select a committee and to then select a leader of the committee.] Combinatory kenneth-rosen discrete-mathematics counting binomial-theorem descriptive + – admin asked Apr 30, 2020 admin 174 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.