Question

A box contains two pair of socks of two colours (black and white). I have picked out a white sock. I pick out one more with my eyes closed. What is the probability that I will make a pair?

Answer 1

No. of socks in the box = 4
Let B and W denote black and white socks respectively.
Then we have:
S = {B,B,W,W}

If a white sock is picked out, then the total no. of socks left in the box = 3
No. of white socks left = 2-1 =1

Probability of getting a white sock

=$\frac{\mathrm{Number}\mathrm{of}\mathrm{white}\mathrm{socks}\mathrm{left}\mathrm{in}\mathrm{the}\mathrm{box}}{\mathrm{Total}\mathrm{no}.\mathrm{of}\mathrm{socks}\mathrm{left}\mathrm{in}\mathrm{the}\mathrm{box}}=\frac{1}{3}$