Click on the links below for each definition/formula:
Present ValueFuture ValueTo Find Interest Rate:
Set the two values equal and solve, given the number of years
For example:
If $10 today is equal to $15 in 4 years, then:
1. 10=15/(1+i)^4
2. 10(1+i)^4 = 15
3. (1+i)^4=1.5
4. 1+i=(1.5)^.25
5. 1+i=1.1067
6. i=.1067
7. i=10.67%
DON’T FORGET RULE OF 72 and RULE OF 128
Example 1:
Your grandmother deposited $100 in a savings account for you on your first birthday. She stipulated that the money was to remain in the account until your 21st birthday. That day has now arrived. The savings account has paid 5.25 percent interest compounded annually since the money was deposited. How much money is now in the account?
PV=$100
i=.0525
n=20
100(1.0525)^20 = $278.25
Example 2:You hear of a surefire money-making scheme which promises that if you invest $1,000 today, you'll receive $2,000 in 10 years. Alternatively you can deposit the $1,000 in a 9.25 percent insured savings account. You wonder what the present value of the promised $2,000 is worth assuming the 9.25 percent interest rate. In other words, is the scheme better than just depositing the money in the savings account?
FV(10) =$2,000
i=.0925
n=10
2000=1/(1.0925)^10 = $825.69
(You are better off putting the money in at the 9.25% interest.)
What rate does the scheme pay? 7.18%