APPLICATIONS OF PERCENT

Percents can be used in solving many types of problems and situations.

In this section, we are going to cover the two most common applications of percent.

They are

1. Finding the total cost

2. Simple interest

Finding the Total Cost

Sales tax, which is the tax on the sale of an item or service, is a percent of the purchase price that is collected by the seller.

Example :

Marcus buys a varsity jacket from a clothing store in Anaheim. The price of the jacket is $80 and the sales tax is 8%. What is the total cost of the jacket ?

Solution : 

Step 1 :

Use a bar model to find the amount of the tax.

Draw a bar for the price of the jacket, $80. Divide it into 10 equal parts. Each part represents 10% of $80, or $8.

Then draw a bar that shows the sales tax: 8% of $80.

Because 8% is 4/5 of 10%, the tax is 5/4 of one part of the whole bar.

Each part of the whole bar is $8.

So, the sales tax is 5/4 of $8.

4/5 × $8 = $6.40

The sales tax is $6.40.

Step 2 : 

To find the total cost of the jacket, add the price of the jacket and the sales tax.

Jacket price + Sales tax = Total cost

$80 + $6.40  =  $86.40

So, the total cost of the jacket is $86.40

Finding Simple Interest

When we deposit money in a savings account, our money usually earns interest. When we borrow money, we must pay back the original amount of the loan plus interest. .

Simple interest is a fixed percent of the principal. The principal is the original amount of money deposited or borrowed.

Example : 

Terry deposits $200 into a bank account that earns 3% simple interest per year. What is the…total amount in the account after 2 years ?

Solution : 

Step 1 :

Find the amount of interest earned in one year. Then calculate the amount of interest for 2 years. 

Write 3% as a decimal : 0.03

Interest rate x Initial deposit  =  Interest for 1 year

0.03 x $200  =  $6

Interest for 1 year x 2 years  =  Interest for 2 years

$6 x 2  =  $12

Step 2 :

Add the interest for 2 years to the initial deposit to find the total amount in his account after 2 years.

Initial deposit  +  Interest for 2 years  =  Total

$200 + $12  =  $212

So, the total amount in the account after 2 years is $212.

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