The number of 9 digit numbers which have all distinct digits, is
10!
9!
8(9)!
10! -9!
The required number of ways
= The number of ways of permuting nine digits out of ten digits 0, 1, 2, …, 9
– The number of ways of permuting nine digits out of nine digits 1, 2, …, 9
=10P9−9P9=10!1!−9!=10!−9!