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APPLICATIONS OF PERCENT Applications of percents is a term that refers to the different ways that percents can be used. • The percent of change refers to the percent an amount either increases or decreases based on the previous amounts or numbers. o The percent of change can be used when determining the percent increase of the cost of any item over time, for example movie tickets, clothing or food. o It can also be used to determine the percent decrease in the value of any item over time such as a car, house or boat. • Calculating discounts and markups are other ways to apply percents in real life applications Applying percents also means to calculate simple interest using the interest equation, I = P · r · t , where P is the principal; r is the rate and time is the time. In this equation, the rate is a percent that is changed to a decimal and then calculated. Estimating with percents is another way to use percents. In some situations, the exact percentage is not needed, but just an estimate. Recognizing what is the approximate percent of a total can be very useful in everyday life. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

How to use applications of percent Percent increase or decrease can be found by using the formula: percent of change = actual change/original amount. The change is either an increase, if the amounts went up or a decrease if the amounts went down. If a number changes from 33 to 89, the percent of increase would be: Percent of increase = (89 -33) ÷ 33 = 56 ÷ 33 ≈ 1.6969 ≈ 170% • When a number decreases, the percent of decrease is found using the same formula. If a number changes from 75 to 55, the percent of decrease would be: Percent of decrease = (75 - 55) ÷ 75 = 20 ÷ 75 ≈ .266667 ≈ 27% A discount is calculated in the same way as a percent of decrease if given the original price and the reduced price. If a jacket was originally $59.99 and is now $34.99, the discount would be: Discount = (59.99 - 34.99)/54.99 = 25/59.99 = .412 ≈ 41% • To find the amount of discount, the percent equation should be used. The percent equation is 'a is p percent of b' or a/b = p/100. This is also the way to solve for a markup. For example, if a dealer buys a car for $15,000 and he sells it to a customer for $22,500, what is the percent of markup? Markup = 22,500/15,000 = x/100 → (2,250,000) = 15000x → x = 150% © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

Simple interest is also calculated using percents. The interest equation, I = P · r · t , is used to find the simple interest when given the principle, rate and time. If interest is given, along with two other values, such as rate or time, inverse operations can be used to solve for the missing value. For example, how long should $1000 be in an account at a rate of 5% in order to earn $200 in interest? Ex. I = P · r · t → 200 = 1000 · 5% · t → 200 = (1000)(.05)t → 200 =50t → 200/50 = t → 4 = t Since t = 4, it means that the money should be in the account for 4 years in order to earn $200 interest. Estimating with percents is another way to use percents. For example, Sue is shopping and she wants to buy a dress that costs $69.99. It is marked 33% off, approximately how much is the discount. Since 10% of 69.99 is about $7, Sue can estimate that she will get ($7)(3) or about $21 off the price of the dress. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.

Try This! 1. What is the percent increase of a gallon of milk that was originally $1.79 and is now $2.29? 2. What is the percent decrease in the value of a boat that originally cost $12,000 and now sells for $8,000? 3. What is the percent discount on a desk that originally cost $99 and now costs $59? 4. If a necklace cost $3.50 to make and now sells for $8.99, what is the percent markup? 5. What is the simple interest using, I = P · r · t: P = $1000, r = 8%, t = 2 years P = $5000, r = 4%, t = 1 year 6. What is the missing value using, I = P · r · t: I = $500, r = 8%, t = 2 years I = $50, P = $2000, t = 1 year 7. If a computer costs $899 and is 23% off, what is the estimated discount? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.