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Chapter 5

Percent

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Solving Commission, Percent of Increase

or Decrease, and Interest Problems

5.5

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Solving Commission Problems

The amount of money a person makes that is a percentage of the value of sales is called a commission. It is calculated by multiplying the percentage (called the commission rate) by the value of the sales.

Commission = commission rate value of sales

Example:A salesperson has a commission rate of 18.5%. He sells $43,250 worth of goods. What is his commission?

= 18.5% $43,250Commission = commission rate value of sales

= 0.185 43,250= 8001.25 His commission is $8,001.25.

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Solving Increase & Decrease Problems

We sometimes need to find the percent by which a number increases or decreases.

Example:The cost of a certain car increased from $16,000 last year to $17,280 this year. What was the percent of increase?

Amount of increase = original amount – new amount

The car’s cost increased by 8%.

amount of increase = original amountPercent of increase

= 17,280 – 16,000 = 1280amount of increasePercent of increase = original amount1280= 16000 = 0.08

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Solving Increase & Decrease Problems

Example:Patrick weighed 285 pounds two years ago. After dieting, he reduced his weight to 171 pounds. What was the percent of decrease in his weight?

Amount of decrease = original amount – new amount

Patrick’s weight decreased by 40%.

amount of decrease = original amountPercent of decrease

= 285 – 171 = 114amount of decreasePercent of decrease = original amount114= 285 = 0.4

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Solving Simple Interest Problems

Interest is money paid for the use of money. The principal is the amount deposited or borrowed. The interest rate is per year, unless otherwise stated. If the interest rate is in years, the time must also be in years.

The interest earned is $1,728.

Interest = principal rate timeI = P R T

Example:Find the simple interest on a loan of $3600 borrowed at 6% for 8 years.

I = P R T= 3600 0.06 8= 1728