# Percentage

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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