In this video, we will be learning how to determine percent change. After you finish this lesson, view all of our Pre-Algebra lessons and practice problems.

Percent Change Formula: \dfrac{New Value - Original Value}{Original Value}\cdot100\%=Percent Change

For example:

The price of gas was originally $5. The new price for gas is $4. What is the percent change?

\dfrac{New Value - Original Value}{Original Value}\cdot100\%=Percent Change

\dfrac{(4) - (5)}{(5)}\cdot100\%=Percent Change\leftarrow Substitute the givens

\dfrac{(4) - (5)}{(5)}\cdot100\%=Percent Change\leftarrow Simplify

\dfrac{-1}{5}\cdot100\%=Percent Change

 

-20\%=Percent Change

Examples of Percent Change

Example 1

The staff at a company went from 40 to 29 employees. What is the percent decrease in staff?

\dfrac{New Value - Original Value}{Original Value}\cdot100\%=Percent Change

First, substitute the given

\dfrac{(29) - (40)}{(40)}\cdot100\%=Percent Change

Then, simplify

\dfrac{-11}{40}\cdot100\%=Percent Change

-27.5\%=Percent Change

Example 2

Jessica works in a candystore for $8.00 per hour. If her pay is increased to $14.00, then what is her percent increase in pay?

\dfrac{New Value - Original Value}{Original Value}\cdot100\%=Percent Change

First, substitute the given

\dfrac{(14) - (8)}{(8)}\cdot100\%=Percent Change

Then, simplify

\dfrac{6}{8}\cdot100\%=Percent Change

75\%=Percent Change

Video-Lesson Transcript

In this video, we will be learning how to determine percent change.

Let’s go through percent increase and percent decrease.

We will use just one formula to compute the percent change:

\dfrac{New Value - Original Value}{Original Value} \times 100\%

For example:

The price of gas was originally \$5. The price went down to \$4. What is the percent change?

Let’s use the formula.

\dfrac{4 - 5}{5} \times 100\%

Which will be \dfrac{(- 1)}{5} \times 100\%

Then divide (- 1) by 5 the answer is (- 0.20)

(- 0.20) \times 100\% = (-20\%)

We have a 20\% decrease.

Percent Change

Let’s have another one.

The price of gas was originally \$4. The price went down to \$5. What is the percent change?

Let’s use the formula and substitute all the given values.

\dfrac{5 - 4}{4} \times 100\% \dfrac{1}{4} \times 100\% 0.25 \times 100\%

We’ll get 25\%

Since the answer is positive, it means it’s an increase.

Just a review, the percent change formula is

\dfrac{New Value - Original Value}{Original Value} \times 100\%