In this video, we will be learning how to find a percent of a number using proportions. After you finish this lesson, view all of our Pre-Algebra and Algebra lessons and practice problems.

In math, **“of”** means **multiply**

Percent Formula:

## Example of Finding the Percent of a Number

What** is** 8% **of** 40?

First we cross-multiply

Then we divide by 100 on both sides to isolate *x*

## Example 1

What **is** **of** ?

First, we cross-multiply

Then, we divide by on both sides to isolate

The answer is

## Example 2

What percent **of** **is** ?

We have the “of” and the “is”. Our formula should look like this:

Let’s cross multiply

is

is

We have:

Now, let’s divide both sides by

Therefore, the answer is

## Video-Lesson Transcript

In this video, we will be learning how to find a percent of a number using proportions.

In math, ‘of’ means ‘multiply’.

So if you’re asked of , it means .

We can’t get the answer right away.

We have to change into a decimal.

So we have to move the decimal two spaces from the right to left.

will become then we can multiply

Another way to find the percent of a number is the percent formula.

Percent formula is

Let’s answer this question:

What is of ?

Let’s use the formula

Let’s cross-multiply

is

is

Now we have

To isolate , let’s do the inverse operation.

We just have to divide both sides by

And we get

Which is the same answer using a different method.

To sum up, you can multiply or use the percent formula to get the answer if the missing value is the “is” or the part.

But if the missing value is the percent or the whole, you have to use the percent formula.

To give an example, let’s answer this question:

What percent of is ?

Here, we’re looking for the percent. We have the “of” and the “is”.

The formula is

Since we’re missing the percent, our formula should look like this

Then let’s cross multiply

is

is

Now, let’s do the inverse operation of multiplication which is division.

So, let’s divide both sides by

The answer is

So the answer to what percent of is ?

The answer is