Finance, Growth & Decay
We extend Grade 10 finance to include nominal and effective interest rates, annuities and future value, and present value calculations.
6.1 Nominal & Effective Interest Rates, Future Value
- Convert between nominal and effective annual rates
- Calculate the future value of periodic payments (annuities)
- Solve for present value and time period
Real-World Connection
A bank advertising '12% p.a. compounded monthly' is NOT the same as '12% per year'. The effective rate is higher because of monthly compounding. Understanding this difference prevents expensive surprises when comparing financial products.
Effective Annual Rate from Nominal
$m$ = number of compounding periods per year; $i_{\text{nom}}$ = nominal annual rate
Future Value of Annuity
$x$ = regular payment, $i$ = interest rate per period, $n$ = number of payments
Present Value of Annuity
The amount needed NOW to fund $n$ future payments of $x$
âšī¸ Note
For monthly payments at annual rate : use and . Always match the frequency of the rate to the frequency of payments.
Worked Example
Effective vs Nominal Rate
Problem
Worked Example
Future Value of Annuity
Problem
CAPS Cognitive Level Distribution