Periodic Compound Interest
Annual Compound Interest
With interest for 1 year...
With interest for 2 years...
With interest for 3 years...
And so on...
Exponential Growth
Annual Interest
Example P = n = i = What values are given? 8 7/100 = 0.07
Calculate the new balance
Try Another
12%, compounded quarterly Consider interest on our $10000 over a one- year period, but now compounded quarterly. Say the 12% is split into quarters so that 3% of interest is earned each quarter. Let i = interest per period = 0.12/4 = 0.03 n = number of times interest is computed = 4 Using the same compound interest formula, the new balance is computed to be
12%, compounded monthly Consider interest on our $10000 over a one- year period, but now compounded monthly. Say the 12% is divided so that 1% of interest is earned each month. Let i = interest per period = 0.12/12 = 0.01 n = number of times interest is computed = 12 Using the same compound interest formula, the new balance is computed to be
Compound Interest Formula:
More frequent is better !
Keeps getting better !
Another Example
Avoid rounding errors !
Yet Another Example
A Different Question? The “Present Value”
Another Example
Comparing Interest Rates
Growth in 1 year?
Effectively, 9.6% Also, called the annual percentage yield (APY). The interest is equivalent to earning 9.6% annually.
Effectively, 9.74% This account has an effective rate, or APY, of 9.74%
Effective Rate Formula
Compare Accounts
Annual Yield Since the effective rate, r e, is the annual yield, use it like annual compounded interest ( m = 1). If a deposit of $8000 earns interest with an APY of 6.8%, what is the value of the account at the end of 5 years? Note an n th root is used to cancel an n th power.
Determining the Yield Suppose an investment of $9000 matures to a value of $12000 over 4 years. Determine the effective rate, r e, The APY is about 7.457%
Determining the Yield If a bond purchased for $700 matures to a value of $1200 over 8 years, what is the effective rate, r e. The APY is about 6.97%