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Find the principal invested if $15,222.57 interest was earned in 6 years at an interest rate of 10.28% .

$24,679.91

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Find the principal invested if $10,953.70 interest was earned in 5 years at an interest rate of 11.04%.

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Find the rate if a principal of $5,400 earned $432 interest in 2 years.

4%

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Find the rate if a principal of $2,600 earned $468 interest in 6 years.

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Find the rate if a principal of $11,000 earned $1,815 interest in 3 years.

5.5%

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Find the rate if a principal of $8,500 earned $3,230 interest in 4 years.

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Solve Simple Interest Applications

In the following exercises, solve the problem using the simple interest formula.

Casey deposited $1,450 in a bank account with interest rate 4%. How much interest was earned in 2 years?

$116

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Terrence deposited $5,720 in a bank account with interest rate 6%. How much interest was earned in 4 years?

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Robin deposited $31,000 in a bank account with interest rate 5.2% . How much interest was earned in 3 years?

$4,836

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Carleen deposited $16,400 in a bank account with interest rate 3.9% . How much interest was earned in 8 years?

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Hilaria borrowed $8,000 from her grandfather to pay for college. Five years later, she paid him back the $8,000 , plus $1,200 interest. What was the rate of interest?

3%

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Kenneth lent his niece $1,200 to buy a computer. Two years later, she paid him back the $1,200 , plus $96 interest. What was the rate of interest?

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Lebron lent his daughter $20,000 to help her buy a condominium. When she sold the condominium four years later, she paid him the $20,000 , plus $3,000 interest. What was the rate of interest?

3.75%

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Pablo borrowed $50,000 to start a business. Three years later, he repaid the $50,000 , plus $9,375 interest. What was the rate of interest?

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In 10 years, a bank account that paid 5.25% earned $18,375 interest. What was the principal of the account?

$35,000

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In 25 years, a bond that paid 4.75% earned $2,375 interest. What was the principal of the bond?

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Joshua's computer loan statement said he would pay $1,244.34 in interest for a 3 year loan at 12.4% . How much did Joshua borrow to buy the computer?

$3,345

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Margaret's car loan statement said she would pay $7,683.20 in interest for a 5 year loan at 9.8%. How much did Margaret borrow to buy the car?

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Caitlin invested $8,200 in an 18-month certificate of deposit paying 2.7% interest. How much interest did she earn form this investment?

$332.10

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Diego invested $6,100 in a 9-month certificate of deposit paying 1.8% interest. How much interest did he earn form this investment?

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Airin borrowed $3,900 from her parents for the down payment on a car and promised to pay them back in 15 months at a 4% rate of interest. How much interest did she owe her parents?

$195.00

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Yuta borrowed $840 from his brother to pay for his textbooks and promised to pay him back in 5 months at a 6% rate of interest. How much interest did Yuta owe his brother?

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Everyday math

Interest on savings Find the interest rate your local bank pays on savings accounts.

  1. What is the interest rate?
  2. Calculate the amount of interest you would earn on a principal of $8,000 for 5 years.

Answers will vary.

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Interest on a loan Find the interest rate your local bank charges for a car loan.

  1. What is the interest rate?
  2. Calculate the amount of interest you would pay on a loan of $8,000 for 5 years.

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Writing exercises

Why do banks pay interest on money deposited in savings accounts?

Answers will vary.

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Why do banks charge interest for lending money?

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

.

On a scale of 1–10, how would you rate your mastery of this section in light of your responses on the checklist? How can you improve this?

Practice Key Terms 4

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Source:  OpenStax, Prealgebra. OpenStax CNX. Jul 15, 2016 Download for free at http://legacy.cnx.org/content/col11756/1.9
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