Question

Tim must choose 4 graphic novels out of a collection of 13 to take on vacation.

In how many ways can he select the graphic novels?

A. 28,561

B. 17,160

C. 715

D. 52

Answer 1

Answer: 715 ( C )

Step-by-step explanation:

C (13,4) = (13!)/(4!*9!)

So it can be done on the calculator by 13C4

13! = 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

4! = 4 x 3 x 2 x 1

9! = 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 / ( 4 x 3 x 2 x 1 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 )

6,227,020,800 / 8,709,120

=715

So the correct answer is C, 715