Question

How do you write 10000 in roman numeral?

Answer 1

In some places it is written as C.

And in some places written as X.

Answer 2

Roman numbers don't have 10000 symbols

But
M = 1000
SO
10000 = MMMMMMMMMM
Which mean M is added 10 times to give 10000

Or

We also know
10 = X


Remember the rule of writing numbers is roman is different from Hindu Arabic numbers

$so \: 10000 \: = \frac{}{x}$
Where the bar above X indicate x multiply by 1000