How many ways are there to choose a three-digit lottery number? Note that numbers like 003, 014, 222, 232 or 123 are all allowed.
This is the fancy permutation formula: You have n items and want to find the number of ways k items can be ordered:
P(n,k) = n!/(n-k)!
n! = n factorial = n * (n-1) * (n-2) * (n-3)... * 1
I'll let you do the calculations.