Question

A 4-digit password is a number that begins with a 3 and does not contain a zero or nine. If digits can be repeated, how many possible passwords are there?
1,536
512
343

Answer 1

so there are three free digets
and each can be one of 8 numerals

Answer 2

\[8^3\]

Answer 3

3 _ _ _ each of the three remaining spaces have 8 possibilities i.e. excluding 0 and 9...So as unkle Rhaukus says its 8*8*8= 512