Question

A lock on a fence door has a 3 digitcombination. Each digit can be anynumber between 1 - 8. The onlyrestriction is that all 4 characters cannotbe the same (e.g. 111, 222, 333, etc.).How many combinations are possible?

Answer 1

we have

Multiply them together you get

$8\cdot8\cdot8=512$

But since all 4 characters cannot be the same, we subtract 8 from 512

$512-8=504$

answer: 504 combinations