Two cards are drawn together from a pack of 52 cards. The probability that one is a spade and one is a heart, is:

Let S be the sample space.

Then, n(S) = $52C2$=(52 x 51)/(2 x 1) = 1326.

Let E = event of getting 1 spade and 1 heart.

n(E)= number of ways of choosing 1 spade out of 13 and 1 heart out of 13 =  $13C1*13C1$ = 169.

P(E) = n(E)/n(S) = 169/1326 = 13/102.