Why are there fifty two cards in a normal pack?

There are 4 suits and each suit has 13 cards. 4 x 13 = 52.

Fun With Math:

Pick a card, any card. Say it's a 7. Chances of drawing a 7 next are 3 out of 51, because thee are now three 7s in the 51-card deck. If you do, chances of drawing another 7 are 2 out of 50, and the fourth one 1 out of 49. So far that's 6 out of 124950 or 1 out of 20825. But that's drawing four cards and getting four of a kind; a fifth card gives you more chances because you are allowed one card that's not a 7 in the first five you draw. How do you deal with that?

OK, let's start over. First card is Y, which may be 7 or any other card. Success (4 of a kind) will be when you draw YYYYX, YYYXY, YYXYY, YXYYY, or YXXXX in order as you draw (X is the first denomination you draw that isn't Y). Each of these five cases has the same 1 out of 20825 chance as what I described above, which is the YYYYX case. Adding the five probabilities up, you get 1 out of 4165, or to put it another way, the odds of 4 of a kind are 4164 to 1 against you.

Isn't Math fun?