Question

six-digit passwords using the digits 0 throgh 9 with repetitionnof digits sllowed

Answer 1

here are 10 numbers in all including 0. The first space can be filled in 9 ways (as we have to exclude 0). The second through sixth spaces can be filled in 10 ways as 0 can be included.
Totally, 9 x 10 x 10 x 10 x 10 x 10 or 9 x 10^5 digits can be formed if repetition is allowed.

Answer 2

if it is a six-digit password why can't we use numbers like

012345