[danielf]

Originally Posted by Damien

We need another challenge, of the Monty Hall Type...

I've got another one. It's a mortgage calculator. Say you have a mortgage of £100,000. Specify an interest rate and monthly repayment amount. What you want to determine is the number of months required to pay off the balance, keeping in mind that you will accrue interest on the outstanding balance. My solution is 8 lines long. You can check your solution against the calculators floating around on the web.