1. SECTION
5-4
Simple Interest pp

2. Section Objective
Calculate:
simple interest

3. Key Words to Know interest (p. 205)
The amount of money paid for the use of a lender’s money.
simple interest (p. 205)
Interest paid only on the principal in a bank account.

4. Key Words to Know principal (p. 205)
The amount of money put into an account, on which interest is based.
annual interest rate (p. 205)
The percent of the principal in a bank account earned as interest based on one year.

5. Formula Interest = Principal × Rate × Time
(Important Note: In this formula, rate is expressed as a decimal, fraction, or percent; time is expressed in years or a fraction of a year.)

6. Understanding the Williams Sisters
p. 205
What is your definition of interest?

7. Example 1
Joyce Tyler deposits $900 in a savings account. The account pays an annual interest rate of 5½ percent. She makes no other deposits or withdrawals. After three months, the interest is calculated.
How much simple interest does her money earn?

8. Example 1 Answer Step: Find the interest at 5½ percent.
Interest = Principal × Rate × Time
$ × 5½% × 3/12
$ × × 0.25 = $ = $12.38

9. Example 2
Lena Green’s bank computes 4 percent interest on a daily basis. She has $1,000 in the account for 10 days. She makes a deposit of $600 and it is in the account for 15 days. She withdraws $400 and the balance earns interest for 6 days. How much interest does she earn? What is the amount in the account at the end of the month?

10. Example 2 Answer
Step: Find the interest at 4 percent for each set of days.
Principal × Rate × Time
(Note: Remember that the time has to be a fraction of a year, so divide the number of days by 365.)

11. Practice 2 Answer (cont.)
$1,000 × 4% × 10/365 = $ = $1.10
($1,000 + $600) × 4% × 15/365 = $2.630 = $2.63
($1,600 – $400) × 4% × 6/365 = $0.789 = $0.79
Total interest for the month is $4.52
Total amount in the account is $1,200 + $4.52 = $1,204.52

12. Practice 1
Victoria Wright deposited $1,500 in a savings account. No other deposits or withdrawals were made. The account paid an annual interest rate of 2 percent.
How much simple interest did her money earn after 6 months?

13. Practice 1 Answer
$15.00

14. Practice 2
Rodolfo Ortega deposited $4,200 in a new savings account. The bank pays 5¼ percent simple interest computed on a daily basis. He made no other deposits or withdrawals.
How much simple interest will his money earn after 214 days?

15. Practice 2 Answer
$129.28

16. END OF SECTION
5-4
Simple Interest