Question

Evaluate.
9!/7!

a) 63
b) 72
c) 81

Answer 1

Cancel.

Answer 2

You can take advantage of the fact that 9! = 9*8*7!

Answer 3

Or you can expand everything out to get

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

and

7! = 7*6*5*4*3*2*1

Answer 4

Canceling is more efficient. Use the observation made via the definition of the factorial by Jim.

Answer 5

which is ??

Answer 6

9!
----
7!

becomes

9*8*7!
-------
7!

and cancels to


9*8
-----
1

Answer 7

or just 9*8

Answer 8

@burakb, please do not post full answers. It's against the Code of Conduct.

Answer 9

Alright
9!=9*8*7*6*5*4*3*2*1 and 7!=7*6*5*4*3*2*1 so
\[9!\div7!=(9*8*7*6*5*4*3*2*1*)\div(7*6*5*4*3*2*1)=9*8=72\]