Question

You have 12 CDs, but only have time to listen to two of them. How many combinations of CDs do you have to choose from?

Answer 1

Total number of CDs = 12
Number of CDs that can be selected at once = 2

Selecting 2 CDs from 12 means combination of 12 objects taken 2 at a time. This can be calculated by 12C2.


`12C2 = (12!)/(2!*(12-2)!) \\ \\ 12C2= (12!)/(2!*10!) \\ \\ 12C2= (12*11)/(2) \\ \\ 12C2=66`

This means, we have 66 possible combinations to choose from