There's always the classic "making change" problem:
What is the least number of coins required to total $x.xx?
Variations on that problem could include:
- Allow the user to input the value of each coin (instead of relying on the assumed values of a penny, nickel, etc)
- Add restrictions on the maximum (or minimum) number of coins available (e.g., you can use no more than one nickel)
- Find a solution that uses some exact number of coins
- Count how many different ways are possible (using any number of coins)
