Compound Interest Essential Skill: Demonstrate Understanding of Concept
Compound Interest Compound Interest What is the difference between simple and compound interest? Simple Interest: Interest that is earned or paid only on the principal. Compound Interest Interest compounded annually means you find the interest after one year and add it to your principal In the second year, the interest becomes part of the principal Continue with this method for the amount of time you invest
Simple Interest: You deposit $50 in a saving account that earns 2% interest. After 3 years how much money is in the account? I=Prt Compound Interest: You deposit $50 in a savings account that earns 2% interest annually. After 3 years how much money is in the account?
How could we find the balance at the end of each year without adding? Multiply by 1.02 Try the same problem this way: Compound Interest: You deposit $50 in a savings account that earns 2% interest annually. After 3 years how much money is in the account?
Principal at start of year Balance at end of year Here is another way to look at the problem: Compound Interest: You deposit $50 in a savings account that earns 2% interest annually. After 3 years how much money is in the account? Principal at start of year Balance at end of year Year 1 $50 A= 50(1+.02) A = $51 Year 2 $51 A = 51(1+.02) A = $52.02 Year 3 $52.02 A = 52.02(1 + .02) A = $53.06
Compound Interest When an account earns interest compounded annually, the balance A is given by the formula: A = P(1 + r)t Where P is the principal, r is the annual interest rate (written as a decimal), and t is the time in years. 1.) You deposit $1,500 into an account that earns 2.4% interest compounded annually. Find the balance after 6 years.
Find the balance using both simple and compound interest for the following: 2.) Simple Compound P = $10,000 P = $10,000 r = 8.5% r = 8.5% compounded annually t = 3 years t = 3 years
Find both simple and compound interest for the following: 3.) Simple Compound P = $500 P = $500 r = 4.25% r = 4.25% compounded annually t = 25 years t = 25 years
Find both simple and compound interest for the following: 4.) Simple Compound P = $1,250 P = $1,250 r = 2% r = 2% compounded annually t = 5 years t = 5 years
What is the account compounds on a time frame shorter than a year? Challenge What is the account compounds on a time frame shorter than a year? A = P (1 + )nt where P = Principal, r = interest rate, t = time in years, and n = number of times per year interest is compounded You deposit $1000 into an account that earns 6% interest compounded semiannually. What is the balance after 4 years? r n
P = $3000, r = 6.2%, t = 7 years, compounded quarterly P = $500, r = 4%, t = 8 years, compounded monthly