Three squares of chess board are selected at random. The probability of getting 2 squares of one colour and other of a different colour is
Total boxes in chess of 8*8= 64.
choosing any 3 squares= 64C3.
Choosing such that we have 2 of one colour and 1 of other colour.
So, 2B and 1W or 1W or 2B. (2 possibilities).
Required probability= (32C2 * 32C1) * 2 / 64C3= 16/21