View All num of num Add Photos Liquid Capital www.liquidcapital.com Unclaimed Profile Overview Reviews Salaries Interviews Jobs Photos Benefits 12 Reviews 8 Salaries 6 Interviews Follow Add Interview Follow Add Interview Interview Question Options Trader Interview London, England (UK) Liquid Capital If there was a drawer in front of me containing 4 socks , either black or white, and I know that I have a 50% probability of pulling out two white socks in a row, then what is the probability of pulling out two black socks? Tags: See more , See less 8 Answer Add Tags Answer Interview Answer 5 Answers ▲ 1 ▼ There is zero probability of pulling two black socks. Interview Candidate on Jul 21, 2010 ▲ 0 ▼ Assuming there are 2 whites and 2 blacks then getting 2 socks of the same colour is the same Anonymous on Aug 23, 2012 ▲ 0 ▼ Above meant to say: Has the same probability Anonymous on Aug 23, 2012 ▲ 0 ▼ You can't assume there are two white socks and two black socks. This problem is an easy enumeration problem actually.From the problem, you have at least 2 white socks, otherwise it would be impossible to take out 2 in a row. So you have either 2 white socks, 3 or 4.Just compute the three prob of getting two white socks in a row for all case and see which is 50%.P(two w in a row| 2 white socks) = (2/4) * (1/3) = 1/6 => not two socks.P(two w in a row| 3 white socks) = (3/4) * (2/3) = 1/2 => this is our answer.Obviously, if there were 4 socks, we would have a 100% chance of getting two whites in a row. So as calculated, there must be 3 white socks. j-dw on Oct 13, 2012 ▲ 0 ▼ The probability is 0 as there is only 1 black sock.Solution:Assume there are k white socks and 4-k black ones in the drawer. =>0.5 = P(2 white socks in a row) = k/4 * (k-1)/3 =>k^2 - k - 6 = 0 =>k = 3 is the number of white socks. qed. Alex on Oct 1, 2013 Interviews > Options Trader > Liquid Capital Add Answers or Comments To comment on this, Sign In or Sign Up.