say a pin number is 5 digits long. The pin number must have one 2 in it anywhere in the pin. How many different combinations can there be?
I believe that there will be 16*10^4 but im not quite sure.
also another one, how many combinations can there be if the 5 digit pin number can only have even digits? I think 5^5, not so sure either though.
thanks.
and one i haven't quite thought about, an even number of even digits. zero even numbers count.