# 8.04 Common percents

Lesson

## Ideas

In previous lessons we learned how to  write fractions as percentages  . Let's practise this concept by looking to the following example.

### Examples

#### Example 1

Express the fraction \dfrac{10}{25} as a percentage.

Worked Solution
Create a strategy

Find the equivalent fraction that has a denominator of 100.

Apply the idea

To get a denominator of 100, we need to multiply 25 by 4 since 25\times 4=100. But if we multiply the denominator by 4 we must also multiply the numerator by 4.

Idea summary

If our denominator is not 100, we can find an equivalent fraction with 100 as the denominator, and then express it as a percentage.

## Common percentages

This video shows us how 10\% is 1 tenth, 25\% is 1 quarter and 50\% is 1 half and uses this to find 10\%,\,25\% and 50\% of values.

### Examples

#### Example 2

What is 50\% of 26?

Worked Solution
Create a strategy

Use the fact that 50\% means half and "of" means multiply.

Apply the idea
Idea summary

When we need to find some common percentages, we can use these to help us:

## Multiples of 10%

Now that you have seen how to find 10\% of an amount, this video shows you how you can find multiples of 10\% of an amount, such as 20\% ,\, 30\% or 80\%.

### Examples

#### Example 3

What is 30\% of \\$40?

Worked Solution
Create a strategy

Find the 10\% and multiply it by 3.

Apply the idea
Idea summary

To find a percentage of a quantity that is a multiple of 10\%, e.g. 20\% ,\, 30\%,\,40\%, we can first find 10\% and then multiply the result.

### Outcomes

#### MA3-7NA

compares, orders and calculates with fractions, decimals and percentages