Two cards are drawn at random from a pack of 52 cards. The probability that one of them is black and other is red is

The number of ways of selecting 2 cards from 52 cards is      n(S)=C(52,2) =52×512 =26×51  Suppose E be the event of getting one red and one black cards from the pack of cardsn(E)= C(26,1)·C(26,1) =26·26Therefore, the probability to the event E is  P(E) = 26×2626×51 =2651