Question

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

Answer 1

120

Explanation:

correct on edge

Answer 2

`_(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`

Explanation:

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

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`