From a pack of 52 cards, 4 cards can be drawn in

52

‌

C4 ways.
There are 13 cards of diamond and 13 cards of spade.
Now, 3 cards of diamond out of 13 cards of diamond can be drawn in

13

‌

C3 ways and 1 card of spade out of 13 cards of spade can be drawn in

13

‌

C1ways.
Thus, the probability of obtaining 3 diamonds and 1 spade card
=

13 ‌ C3× 13 ‌ C1

52 ‌ C4