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Lesson Menu. Main Idea and New Vocabulary NGSSS Example 1:Find Simple Interest Example 2:Find the Interest Rate Example 3:Find the Total Amount Five-Minute Check. Solve problems involving simple and compound interest. interest simple interest principal compound interest.

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#### Presentation Transcript

Main Idea and New Vocabulary

NGSSS

Example 1:Find Simple Interest

Example 2:Find the Interest Rate

Example 3:Find the Total Amount

Five-Minute Check

• Solve problems involving simple and compound interest.

• interest

• simple interest

• principal

• compound interest

### Main Idea/Vocabulary

MA.8.A.6.4 Perform operations on real numbers (including integer exponents, radicals,percents, scientific notation, absolute value, rational numbers, and irrational numbers) using multi-step and real world problems.

### NGSSS

Find Simple Interest

Find the simple interest for \$2,000 invested in a savings account at 5.5% for 4 years.

I = prtWrite the simple interest formula.

I = 2,000● 0.055● 4Replace p with 2,000, r with 0.055, and t with 4.

I = 440

Answer: The simple interest is \$440.

### Example 1

Find the simple interest for \$980 invested in a savings account at 4.5% for 3 years.

A.\$44.10

B.\$132.30

C.\$1,112.30

D.\$1,323.00

### Example 1 CYP

Find the Interest Rate

LOANS Callie borrowed \$4,500 from a bank to pay part of her college tuition. She will repay the loan by paying \$120 a month for the next four years. Find the simple interest rate of the loan.

First find the total that Callie will pay.

\$120 ● 48 = \$5,760 4 years = 48 months

She will pay \$5,760 – \$4,500 or \$1,260 in interest. So, I = 1,260.

### Example 2

1,260

Divide each side by 18,000.

Find the Interest Rate

I= prtWrite the simple interest formula.

1,260= 4,500● r ● 4Replace I with 1,260, p with 4,500, and t with 4.

1,260= 18,000r Simplify.

0.07= rSimplify.

Answer: The simple interest rate is 0.07 or 7%.

### Example 2

LOANS Samantha borrowed \$7,200 from a bank to pay for a used car. She will repay the loan by paying \$236 a month for the next three years. Find the simple interest rate of the loan.

A.1.18%

B.6%

C.6.6%

D.18%

### Example 2 CYP

Find the Total Amount

SAVINGS How much money is in an account where \$80 is invested at an interest rate of 6% compounded annually for 3 years?

Find the amount of money in the account at the end of the year 1.

I= prtWrite the simple interest formula.

I= 80● 0.06● 1Substitution

I= 4.8 Simplify.

80 + 4.80 = 84.80 Add the amount invested and the interest.

### Example 3

Find the Total Amount

Find the amount of money in the account at the end of year 2.

I= prtWrite the simple interest formula.

I= 84.80● 0.06● 1Substitution

I= 5.088Simplify.

84.80 + 5.09 = 89.89 Add the amount invested and the interest.

### Example 3

Find the Total Amount

Find the amount of money in the account at the end of year 3.

I= prtWrite the simple interest formula.

I= 89.89● 0.06● 1Substitution

I= 5.3934Simplify.

Answer:After 3 years there is \$89.89 + \$5.39 or \$95.28.

### Example 3

SAVINGS How much money is in an account where \$310 is invested at an interest rate of 5.5% compounded annually for 3 years?

A.\$327.05

B.\$345.04

C.\$361.15

D.\$364.02

### Example 3 CYP

Find the simple interest to the nearest cent.\$300 at 4% for 2 years

A.\$8.00

B.\$12.00

C.\$24.00

D.\$240.00

### Five Minute Check 1

Find the simple interest to the nearest cent.\$750 at 6.25% for 6 months

A.\$23.44

B.\$37.50

C.\$46.88

D.\$234.38

### Five Minute Check 2

Find the total amount in the account to the nearest cent if the interest is compounded annually.\$1,250 at 7% for 2 years

A.\$1,337.50

B.\$1,425.00

C.\$1,431.13

D.\$2,675.00

### Five Minute Check 3

Find the total amount in the account to the nearest cent if the interest is compounded annually.\$600 at 4.75% for 18 months

A.\$628.50

B.\$642.75

C.\$643.43

D.\$942.75

### Five Minute Check 4

Sam borrowed \$5,000 at 11% simple interest for two years. He made no payments during those two years. How much interest is owed at the end of those two years?

A.\$110.00

B.\$550.00

C.\$610.50

D.\$1,100.00

### Five Minute Check 5

Anna decided to invest \$1,500 at 2.5% simple interest for six months. How much interest does her investment earn?

A.\$18.75

B.\$37.50

C.\$187.50

D.\$225.00