Do you like to ride roller coasters? Take a look at this dilemma.

At an amusement park there is an average of 30,000 visits daily. Over 75% of those people ride on the biggest roller coasters. About how many people ride the roller coasters?

**
To figure this out, you will need to find the percent of a number. Pay attention and you will know how to solve this problem by the end of the Concept.
**

### Guidance

We said that percent are very useful. Part of the usefulness is being able to find percentages of a number. In other words, if you are planning a barbecue and the butcher tells you that 30% of the people want chicken…well, how many people is that? For how many people should you buy chicken?

**
The key words here are “of a number” this means that you multiply to solve the problem. We can convert the percent to a decimal and multiply or convert it to a fraction and multiply.
**

Let’s suppose that you invited 58 people to the barbecue. If 30% prefer chicken, then we need to know how many people that is.

**
First, convert 30% to either a decimal or a fraction
**

\begin{align*}30\% = .30 \ or \ 30\% = \frac{30}{100} = \frac{3}{10}\end{align*}

**
Using the decimal or fraction, you now multiply by the number of people you invited:
@$\begin{align*}.30 \times 58 = 17.4\end{align*}@$
or about 17 people
**

Or

@$\begin{align*}\frac{3}{10} \times 58 = \frac{174}{10} = 17.4\end{align*}@$ or about 17 people.

**
This is the answer.
**

Solve each problem.

#### Example A

What is 20% of 18?

**
Solution: 3.6
**

#### Example B

What is 25% of 40?

**
Solution: 10
**

#### Example C

What is 5% of 80?

**
Solution: 4
**

Now back to the dilemma from the beginning of the Concept.

First, let's write a statement about the problem.

We need to figure out 75% of 30,000.

To do this, first convert 75% to a decimal.

@$\begin{align*}75\% = .75\end{align*}@$

Next, multiply.

@$\begin{align*}.75 \times 30,000 = 22,500\end{align*}@$

**
22,500 people ride the roller coasters.
**

### Guided Practice

Here is one for you to try on your own.

A survey stated that 15% of the people surveyed like olives. Out of the 500 people surveyed, about how many like olives?

**
Solution
**

First, let's write a statement describing the problem.

15% of 500

Now change the percent to a decimal.

@$\begin{align*}15\% = .15\end{align*}@$

Next, multiply.

@$\begin{align*}.15 \times 500 = 75\end{align*}@$

**
75 of the people like olives.
**

### Video Review

### Explore More

Find the percent of the given number by converting the percent to a decimal. You may round if necessary.

- 30% of 90
- 3% of 12
- 14% of 900
- 33% of 99
- 18% of 100
- 8% of 72
- 11% of 50
- 14.5% of 30
- 12% of 80
- 2% of 800
- 150% of 21
- 45% of 60

Read the following situations carefully and answer the questions accordingly.

- For every paycheck you receive, your employer pays 6% to social security. Write this percent as a ratio with a denominator of 100.
- What is 30% of 500?
- A store did a survey and found that @$\begin{align*}\frac{4}{5}\end{align*}@$ of its customers have shopped at its competitors’ stores within in the previous month. What percent is that?