What is 1000!-999!

So it is Heureka.

I had to think about that one  :))

$$\\99.9\% \;\;of\;\;1000!\\\\
=\frac{999}{1000}*1000!\\\\
=\frac{999}{1000}*1000*999!\\\\
=999*999!\\\\$$

Notice that

n! - (n -1 ) !   =

[n x (n-1) x (n-2) x.......x 3 x 2 x 1 ]  - [ (n-1) x (n-2) x.......x 3 x 2 x 1 ]

And factoring out the common term, we have

[ (n-1) x (n-2) x.......x 3 x 2 x 1 ] [n  - 1]  =

[n-1]! * [n-1]

So....... 1000! - 999! =

999! * (999)       ......whatever that is !!!  (it's huge, to be sure)

Chris is of course correct.  He just makes it look hard LOL

1000!=999!x1000

so

1000!-999!

= 999!x1000 - 999!x1

          I can factor out the 999!

=999!(1000-1)

=999! x 999

It's math....it's supposed to look hard......if it looked easy.......the questioners would be on to us!!!!! LOL!!!

What is 1000!-999!  Its 99.9% of 1000!

= 4.0198487281701667977015873148908e+2567

Very fine Melody!