Question

A stack of 9 different cards are shuffled and spread out face down. If 4 cards are tired face up, how many different 4-card combinations are possible?

Answer 1

126.

Explanation:

This is the number of combinations of 4 cards from 9 cards:

= 9C4

= 9! / 4! 5!.

A quick way of calculating this is

9*8*7*6

----------- = 9*2*7 = 126 combinations.

4*3*2*1