2020 AMC 8 Problems/Problem 12

Revision as of 23:53, 17 November 2020 by Iirishabii (talk | contribs)

Solution 1

Notice that $5!$ = $2*3*4*5,$ and we can combine the numbers to make a bigger factorial. To change $9!$ to $10!,$ we need to multiply $9!$ by $2*5,$ which equals $10!.$ Therefore, we have

\[10!*12=12*N!.\] After canceling the $12s,$ we have

\[10!=N!.\] Thus, $N=10(A).$

-iiRishabii