[SOLVED] fundamental counting principal.

I am alright at the questions where you are told how many objects there are, and are asked how many combinations there are of those objects. My question is what about when it says something like....

"A car liscence plate consists of **up to** 6 characters" with any combo of the letters a-1 and numbers 0-9"

or

A room key for a hotel has a 5 by 10 array where a hole is either punched or let solid, how many different room keys are possible."

*I'm not necessarily asking you to solve both questions, I just dont know how you do a question where it could be 1 digit on a plate or 6.

Thanks.