Percent increase and percent decrease are the two types of percent change. This article focuses on percent decrease.
What is Percent Decrease?
Percent decrease is a ratio that compares 2 values. It describes the decline in value of something by a specific rate. Percent decrease is evident anytime a number or amount decreases.
When is Percent Decrease Calculated in the Real World?
- A school principal is comparing student attendance from one semester to another.
- A cell phone company is comparing the number of February text messages to March text messages.
Example: The original price for a bag of apples is $3. On Tuesday, the bag of apples sells for $1.80. What is the percent decrease?
Careful, do not find the difference between $3 and $1.80 and say that the percent decrease is $1.20.
Use this formula to find the percent decrease.
Percent decrease = (Older – Newer) ÷ Older.
= (3 – 1.80) ÷ 3
= .40 = 40%
Note: To convert a decimal into a percent, move the decimal point twice and stick a percent sign (%) at the end.
Percent Decrease is Given
In other situations, the percent decrease is known, but the newer value is unknown.
Example 1: Best Bargain wants to sell a laptop computer for $600 to Alan. J’s Electronics will sell the computer to Alan for 20% less than Best Bargain.
1. How much money will Alan save when he buys the computer from J’s Electronics instead of Best Bargain?
Multiply .20 and $600. Alan will save $120.
2. How much will Alan pay for the computer at J’s Electronics?
$600 – $120 = $480
Example 2: A dress regularly sells for $150. A green tag, marked 40% off, is attached to the dress.
1. What is the discount? .40 * $150 = $60
2. What is the sale price? $150 - $60 = $90
Exercises
Find the percent decrease for exercises 1 through 3.
1. Ice cream
Original: $4.00
Current: $3.50
Percent decrease:
2. Shredded cheese
Original: $2.50
Current: $1.25
Percent decrease:
3. Bottled Water
Original: $1.00
Current: $.75
Calculate the discount, in dollars, for the items in exercises 4 - 6.
4. A box of frozen fish sticks is originally $4.00. This week, it is discounted 33% off the original price.
Discount:
5. A lemon pound cake originally costs $6.00. This week, it is discounted 20% off the original price.
Discount:
6. A Halloween costume costs $30.00. The discount rate is 60%.
Discount: