Finite Math Question

If all digits were different, the number of 10 digit numbers formed is 10!
However, same digits forming the same 10 digit numbers are counted once only, so those possible permutations of 10 digit numbers formed by using same digits are to be retreated, this is applicable to the three digits 1, 2, 3.

The number of distinct 10 digit numbers formed
= 10! / (3! 3! 2!)
= 10x9x8x7x6x5x4x3x2x1 / (3x2x1 x 3x2x1 x 2x1)
= 3,628,800 / 72
= 50,400