1. Five-Minute Check (over Lesson 5–9) Main Idea and Vocabulary
Example 1: Find Simple Interest
Example 2: Test Example: Find the Total Amount
Example 3: Real-World Example: Find the Interest Rate
Lesson Menu

2. Solve problems involving simple interest.
principal
Main Idea/Vocabulary

3. Find the simple interest for $2,000 invested at 5.5% for 4 years.
Find Simple Interest
Find the simple interest for $2,000 invested at 5.5% for 4 years.
I = prt Write the simple interest formula.
I = 2000 ● ● 4 Replace p with 2,000, r with , and t with 4.
I = 440 The simple interest is $440.
Answer: $440
Example 1

4. Find the simple interest for $1,500 invested at 5% for 3 years.
B. $175
C. $215
D. $225 A B C D
Example 1

5. year. Find the Total Amount
Find the total dollar amount in an account where $80 is invested at a simple annual interest rate of 6% for 6 months.
A. $41.20 B. $82.40 C. $84.80 D. $108.80
Read the Item
You need to find the total amount in an account. Notice that the time is given in months. Six months is
year.
Example 2

6. I = prt Simple interest formula
Find the Total Amount
Solve the Item
I = prt Simple interest formula
I = 2.4 Simplify.
Answer: The amount in the account is $80 + $2.40 or $ The answer is B.
Example 2

7. Find the total amount of money in an account where $60 is invested at 8% for 3 months.
B. $61.20
C. $62.20
D. $62.30 A B C D
Example 2

8. The loan will be for 48 months or 4 years. So, t = 4.
Find the Interest Rate
LOANS Gerardo borrowed $4,500 from his bank for home improvements. He will repay the loan by paying $120 a month for the next four years. Find the simple interest rate of the loan.
Use the formula I = prt. To find I, first find the total amount of money Gerardo will pay.
$120 ● 48 = $5,760
He will pay $5,760 – $4,500 or $1,260 in interest. So, I = 1,260. The principal is $4,500. So, p = 4,500.
The loan will be for 48 months or 4 years. So, t = 4.
Example 3

9. I = prt Write the simple interest formula.
Find the Interest Rate
I = prt Write the simple interest formula.
1,260 = 4,500 ● r ● 4 Replace I with 1,260, p with 4,500, and t with 4.
1,260 = 18,000r Simplify.
Divide each side by 18,000.
0.07 = r
Answer: The simple interest rate is 7%.
Example 3

10. LOANS Jocelyn borrowed $3,600 from her bank for home improvements
LOANS Jocelyn borrowed $3,600 from her bank for home improvements. She will repay the loan by paying $90 a month for the next five years. Find the simple interest rate of the loan.
A. 7.5%
B. 10%
C. 12%
D. 13.5% A B C D
Example 3

11. (over Lesson 5-8)
Find the percent of change. Round to the nearest tenth if necessary. State whether the percent of change is an increase of a decrease. original: 25 new: 28
10.7%; increase
B. 10.7%; decrease
C. 12%; increase
12%; decrease A B C D
Five Minute Check 1

12. (over Lesson 5-8)
Find the percent of change. Round to the nearest tenth if necessary. State whether the percent of change is an increase or a decrease. original: 47 new: 36
A. 23.4%; decrease
B. 23.4%; increase
C. 30.6%; decrease
D. 30.6%; increase A B C D
Five Minute Check 2

13. (over Lesson 5-8)
Find the selling price for a book if the cost to the store is $65 and the markup is 30%.
A. $45.50
B. $46.15
C. $84.50
D. $95 A B C D
Five Minute Check 3

14. Find the sale price of a $120 lamp that is on sale for 15% off.
(over Lesson 5-8)
Find the sale price of a $120 lamp that is on sale for 15% off.
A. $102.00
B. $112.00
C. $128.00
D. $138.00 A B C D
Five Minute Check 4

15. A $350 grill is on sale for 25% off. Find the sale price.
(over Lesson 5-8)
A $350 grill is on sale for 25% off. Find the sale price.
A. $437.50
B. $364.00
C. $336.62
D. $262.50 A B C D
Five Minute Check 5

16. (over Lesson 5-8)
Find the amount of discount for a $28 shirt that is on sale for 65% off the original price.
A. $9.80
B. $18.20
C. $20.20
D. $65.00 A B C D
Five Minute Check 6

17. End of Custom Shows