## 4.3 Modelling Compound Interest Systems with Regular Withdrawals using Technology

Note: if you cannot remember how to model reducing balance relations with regular repayments, revise notes for 4.1 Modelling Compound Interest Systems with Regular Withdrawals.

### Guide to Analysing Compound Interest Equations with Regular Withdrawals using Technology (Casio Graphics Calculator)

Note: if you cannot remember how to use the Casio Financial Calculator, revise notes for 3.3 Modelling Reducing Balance Systems with Regular Repayments using Technology.

- The
**annual interest rate**should be entered/calculated as a**positive**value. - The
**initial value (PV)**should be entered/calculated as a**negative**value (remember we justify this by saying we must lose this amount to create the account).