Q21. - Algebra 1

Question

State whether each percent of change is a percent of increase or a percent of decrease. Then find the percent of change. Round to the nearest whole percent.

original: 21 hours  

new: 40 hours

Step-by-Step Solution

Answer

This is the percent of decrease. The percent of change is 90%.

Step 1. Use the definition of the percentage change.

The percent change is the increase or decrease in the value of a quantity. If the new value is larger than the original value then it is a percent increase and if the change in value is lesser than the original value it is called percentage decrease.

Step 2. Example of the percentage change.

For example, if a person has 25 dollars and he gets 3 more dollars and now has 28 dollars, its percentage increase is calculated as shown:

 $\begin{array}{l}\text{Increase }=28-25=3\\ \%\text{ change = r, then}\\ \frac{3}{25}=\frac{r}{100}\\ r=\frac{3}{25}\times 100\\ =12\%\end{array}$

Step 3. Find the percentage change.

We are given that

Original:11 feet 

new: 25 feet

This is a percent of decrease because the new amount is less than the original.

We find the amount of change. And calculate the percentage change as follows:

$\begin{array}{l}\text{Change }=40-21=19\\ \%\text{ change = r, then}\\ \frac{19}{40}=\frac{r}{100}\\ r=\frac{19}{40}\times 100\\ \text{r = \%change = 0.9047}\times 100\\ \text{\%change = 90.47}\\ \approx 90\text{\%}\end{array}$

This is the percent of decrease. Rounding answer off to the nearest whole number, Percent of change is 90%.