Consider a deck of cards:
how many different 4-card hands can have each card from a different suit?

O nasty !  What a delightful little problem !

The first card can be any one of the 52 in the deck.  For each one ...
The second card can be any one of the 39 in the other 3 suits. For each one ...
The third card can be any one of the 26 in the other 2 suits.  For each one ...
The fourth card can be any one of the 13 in the last suit.

Total possible ways to draw them = (52 x 39 x 26 x 13) = 685,464 ways.

But wait !  That's not the answer yet.

Once you have the 4 cards in your hand, you can arrange them
in (4 x 3 x 2 x 1) = 24 different arrangements.  That tells you that
the same hand could have been drawn in 24 different ways.  So
the number of different 4-card hands is only ...

                     (685,464) / (24) = 28,561 hands.

I love it !