How do you simplify (15!)/(2!7!)15!2!7!?

1 Answer
Dec 13, 2016

We can rewrite as
15! = 15xx14! = 15xx14xx13! .. 15!=15×14!=15×14×13!.. and so on
So 15=15xx14xx13xx12xx11xx10xx9xx8xx7!15=15×14×13×12×11×10×9×8×7!

And so,
(15!)/(2!7!) = (15xx14xx13xx12xx11xx10xx9xx8xx7!)/(2!7!) 15!2!7!=15×14×13×12×11×10×9×8×7!2!7!
\ \ \ \ \ \ \ \ = (15xx14xx13xx12xx11xx10xx9xx8)/(2!)
\ \ \ \ \ \ \ \ = (15xx14xx13xx12xx11xx10xx9xx8)/(2)
\ \ \ \ \ \ \ \ = 129739600