The tutor shows how to use the Texas Instruments BA-35 to find the interest rate of a loan.

Example:

Suppose a loan is made for $750. Twenty months later, it is repaid with a lump sum of $880. What is the interest rate, assuming it was compounded monthly?

Solution:

1. To clear the calculator, go into STAT mode then back into FIN mode: press 2nd FRQ 2nd N
2. Key in 750 PV 20 N 880 FV 0 PMT CPT %i
3. Hopefully you receive the answer 0.8024459. This is the interest rate per period, which means per month in this case.
4. Multiply the answer by 12 to arrive at 9.6293502. This means the interest rate is 9.629% compounded monthly.

HTH:)

Source: BA-35 Solar Quick Reference Guide

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.