Sock Drawer

[irchans]

A drawer contains red socks and black socks. When two socks are drawn at random, the probabilitiy that both are red is 1/2. (a) How small can the number of socks in the drawer be? (b) How small if the black socks is even? (c) How small if there are at least 30 socks?


Please put answer-a) or answer-b) or answer-c) in the subject if you post an answer.




(Mosteller)