We can convert a percentage to a decimal number by dividing by $100$.

Therefore, $5\%=\dfrac{5}{100}=5:100=0.05$.

Examples

$28\%=0.28$

$77\%=0.77$

When we convert percentages to decimals, we can calculate how much a particular $\blue{\text{percentage}}$ is of a $\green{\text{number}}$.

For example, $\blue{28}\%$ of $\green{2600}$ equals: $0.28 \times \green{2600}=728$.

In general, we can state the following:

To calculate a certain $\blue{\textit{percentage}}$ of a $\green{\textit{number}}$, we calculate:

$\frac{\blue{\textit{percentage}}}{100} \times \green{\textit{number}}$

Example

How much is $\blue{59}\%$ of $\green{600}$?

$$\begin{array}{rcl}\\ \dfrac{\blue{59}}{100} \times \green{600}&=&0.59 \times \green{600} \\ &=& 354\end{array}$$

We also want to be able to calculate what percentage a specific $\blue{\text{part}}$ is of a specific $\green{\text{whole}}$. Suppose we have a group of $\green{79}$ people. $\blue{19}$ people have blue eyes, and we want to know what percentage of the group has blue eyes.

The entire group of $\green{79}$ people equals $100\%$.

Therefore, $1$ person is $\frac{1}{\green{79}}\times 100\% \approx 1.27\%$.

To calculate what percentage $\blue{19}$ people is, we multiply $\frac{1}{\green{79}}\times 100\%$ by $\blue{19}$. Therefore, $\blue{19}$ of $\green{79}$ equals: $\frac{\blue{19}}{\green{79}} \times 100 \%\approx 24.05\%$

In general, we can state:

To calculate what percentage a specific $\blue{\textit{part}}$ is of a specific $\green{\textit{whole}}$, we calculate:

$\frac{\blue{\textit{part}}}{\green{\textit{whole}}} \times 100\%$

Examples

$$\begin{array}{rcl}\blue{18} &\text{ of} & \green{29} \\&\text{ equals }& \\ \dfrac{\blue{18}}{\green{29}} \times 100\% &\approx& 62.1\% \\ \\ \\ \\ \blue{52} &\text{ of }&\green{128}\\&\text{ equals }& \\\dfrac{\blue{52}}{\green{128}} \times 100\% &\approx &40.6\%\end{array}$$