There was a blind man. He had four socks in his drawer either black or white. He opened it and took out two socks. Now the probability that it was a pair of white socks is 1/2.
Can you find out the probability that he had taken out a pair of black socks ?
How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started?