Percent Change

What is Percent Change?
Percent change measures how much a quantity increases or decreases relative to its original value, expressed as a percentage.

The following diagram gives the formula to find percent change. Scroll down the page for more examples and solutions.

Percent Worksheets
Practice your skills with the following percent worksheets:
Online & Printable Percent Worksheets

Steps to using the percent change formula
Percent Increase
Example: A product’s price rose from $50 to $70. What’s the percent increase?

1. Find the difference (New - Old): 70 - 50 = 20
   
2. Divide by the original value (Old): \( \frac{20}{50} \) = 0.4
   
3. Multiply by 100%: 0.4 × 100% = 40% increase
   

Percent Decrease
Example: A company’s employees dropped from 200 to 150. What’s the percent decrease?

1. Find the difference (New - Old): 150 - 200 = -50
   
2. Divide by the original value (Old): \( \frac{-50}{200} \) = -0.25
   
3. Multiply by 100%: -0.25 × 100% = 25% decrease
   

Common Mistakes to Avoid
❌ Using the wrong denominator: Always divide by the original (old) value.
❌ Ignoring negative signs: A negative result means decrease (no need to say “-10% decrease” just say “10% decrease”).

Percent of Change
This video explains how to determine percent of change: Percent Increase and Decrease

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Percent Increase and Decrease Word Problems
This video explains how to calculate the percent of change using the percent increase and decrease formula.

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Calculating Percent Change Using Equivalent Fractions
Percent change can be calculated by setting up an equivalent fraction (proportion) comparing the change in value to the original value.

Here are the steps:

1. Find the Change in Value
   Change = New Value − Original Value
   (Negative result means a decrease.)
   
2. Set Up the Equivalent Fraction
   \( \frac{Change}{Original Value} \) = \( \frac{x}{100} \)
   (Where \( x \) is the percent change.)
   
3. Solve for \( x \) (Percent Change)
   Cross-multiply and simplify:
   \( x \) = \( \frac{Change}{Original Value} \) × 100
   

Here are some videos that use equivalent fractions to find percent change.
Percent Change
Solving Percent Change Problems

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