0 votes 0 votes Approach : 1. Select given number say 1, then find combination of rest of the elements. e.g select 1 , now remaining 4 elements, make subsets of 2 elements and add "1" in each subsets ie C(4,2) = 6. Suggest any another method please. HeadShot asked Jan 8, 2019 HeadShot 406 views answer comment Share Follow See all 3 Comments See all 3 3 Comments reply Shobhit Joshi commented Jan 8, 2019 reply Follow Share We want to find in how many subset of size $m$ of $n$ elements the element $x$ is present. for every size $m$, one element is fixed $i.e.$ x , so we have $m-1$ spaces to fill and $n-1$ elements left, so, the sets would be ${}^{n-1}C_{m-1}$ 0 votes 0 votes HeadShot commented Jan 8, 2019 reply Follow Share @Shobhit Joshi the same i explained as Approach 1. I need some other method if any. ( Please read the question along with explanation given under question ) 0 votes 0 votes Shobhit Joshi commented Jan 8, 2019 reply Follow Share @HeadShot my bad. 0 votes 0 votes Please log in or register to add a comment.