THIS WILL CALCULATE: If you know the loan amount and the periodic payments, this will calculate your return on investment.

EXAMPLE: You are willing to loan me $35,000 and I will pay you back in equal payments of $800 per month, for 5 years, what is your rate of return on this investment. (or in otherwords, what interest rate am I paying)

See how to calculate this example on a: HP12C  or  HP10B