Question

A librarian chooses seven holiday books from a selection of ten to be displayed in the window of the library. In how many different ways can she choose the group of seven books?

Answer 1

120

Step-by-step explanation:

Answer 2

120

Step-by-step explanation:

This is a combination of 10 objects chosen 7 at a time:

`_(10)C_7=(10!)/(7!(10-7)!)\\\\=(10!)/(7!3!)=(10* 9* 8* ...)/((7* 6* 5*...)(3* 2* 1))\\\\=(10* 9* 8)/(3* 2* 1)=(720)/(6)=120`