Finding a Percent of a Number

Finding a Percent of a Number

Using Word Problems to set up a proportional equation

Setting up a Proportional Equation

 $\frac{part}{total}\ =\ \frac{\%}{100}$  

Set this up as a proportion

Suppose there are 20 questions on a multiple-choice test. If 25% of the answers are choice B, how many of the answers are NOT choice B ?

Multiple Choice

Suppose there are 20 questions on a multiple-choice test. If 25% of the answers are choice B, how many of the answers are NOT choice B ?

• $\frac{x}{20}=\frac{25}{100}$

• $\frac{20}{x}=\ \frac{25}{100}$

• $\frac{20}{100}=\frac{x}{100}$

Set this up as a proportion

Jerry, an electrician, worked 7 months out of the year. What percent of the year did he work ?

Multiple Choice

Jerry, an electrician, worked 7 months out of the year. What percent of the year did he work ?

•  $\frac{7}{100}=\frac{x}{100}$ 

•  $\frac{7}{12}=\ \frac{x}{100}$ 

•  $\frac{12}{7}=\frac{x}{100}$ 

Set this up as a proportion

There are 28 students in a class. Sixteen of those students are men. What percent of the class are women ?

Multiple Choice

There are 28 students in a class. Sixteen of those students are men. What percent of the class are women ?

•  $\frac{16}{28}=\frac{x}{100}$ 

•  $\frac{16}{100}=\ \frac{x}{100}$ 

•  $\frac{12}{28}=\frac{x}{100}$ 

Set this up as a proportion

A metal bar weighs 8.15 ounces. 7.533 ounces of the bar is silver. What percent of the bar is silver ?

Multiple Choice

A metal bar weighs 8.15 ounces. 7.533 ounces of the bar is silver. What percent of the bar is silver ?

•  $\frac{7.533}{8.15}=\frac{x}{100}$ 

•  $\frac{8.15}{7}=\ \frac{x}{100}$ 

•  $\frac{7.533}{100}=\frac{x}{100}$ 

Set this up as a proportion

A customer put $580 into their savings account for one year. What is the bank's rate of interest if the customer earned $37.70 for the year ?

Multiple Choice

A customer put $580 into their savings account for one year. What is the bank's rate of interest if the customer earned $37.70 for the year ?

•  $\frac{580}{100}=\frac{x}{100}$ 

•  $\frac{37.70}{580}=\ \frac{x}{100}$ 

•  $\frac{580}{37.70}=\frac{x}{100}$