1 votes 1 votes Balaji Jegan asked Dec 10, 2018 Balaji Jegan 252 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply srestha commented Dec 11, 2018 reply Follow Share $\sum_{i=1}^{\infty}iP\left ( X\geq i \right )=1.P\left ( 1 \right )+2P\left ( 2 \right )+......$ it is nothing but mean of random variable whose sum is $=1$ https://gateoverflow.in/239388/random-variable 0 votes 0 votes Shubhanshu commented Dec 11, 2018 reply Follow Share Above is the aggregate form of Expectation i.e. $E[x] = \sum^{\infty}_{i=1}iP(i)$ And in the question it is already given that $E[x] = 1.$. So, A should be the answer. 0 votes 0 votes Please log in or register to add a comment.