Frequent use of expressions that reflect increases or decreases in prices, numbers or quantities, always based on 100 units. Some examples:

Gasoline increased by 15%.

It means that every $ 100 there was an increase of $ 15.00.The customer received a 10% discount on all goods.

This means that for every $ 100 a discount of $ 10 was given.Of the players who play at Grêmio, 90% are star players.

It means that out of every 100 players who play at Grêmio, 90 are stars.

## Centesimal reason

All the reason that has for the number 100 consequent is denominated **centesimal reason**. Some examples:

We can represent a centesimal ratio in other ways:

The expressions 7%, 16% and 125% are called **centesimal rates** or **percentage rates**.

Consider the following problem:

John sold 50% of his 50 horses. How many horses did he sell?

To solve this problem, we must apply the percentage rate (50%) on the total horses.

Soon he sold 25 horses, which represents the **percentage** wanted. So we come to the following definition:

**Percentage**is the value obtained by applying a percentage rate to a given value.

## Examples

Calculate 10% of 300.

Calculate 25% of 200kg.

Therefore, 50kg is the value corresponding to the percentage sought.

## Exercises

1) A soccer player over a championship charged 75 fouls, turning 8% of those fouls into goals. How many foul goals has this player scored?

Therefore the player made 6 foul goals.

2) If I bought a club stock for $ 250 and resold it for $ 300, what is the percentage rate of profit earned?

We set up an equation, where adding the initial $ 250.00 with the percentage that increased from that $ 250.00, results in the $ 300.00.

Therefore, the percentage rate of profit was 20%.

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