If you are dealt 4 cards from a shuffled deck of 52 cards, find the probability of getting two queens and two kings.
Divide the deck into three groups, the queens, the kings, and the rest of the deck.
You need to get two of the four queens -- which occurs in 4C2 = 6 ways.
You need to get two of the four kings -- which also occurs in 4C2 = 6 ways.
You need to get none of the rest of the deck -- which occurs in 48C0 = 1 way.
Multiplying these together gives you the various ways that you can get these four cards = 6 x 6 x 1 = 36 ways.
To find the probability that this will occur, we need to find the number of ways that 4 cards can be chosen from 52 cards -- which occurs in 52C4 = 270725 ways -- and divide 36 by 270725 to get the answer.