In cases where a ratio is compared in different units, such as speed, telephone tariff, among others. This ratio (division or quotient), which is a rational number, is called rate. Common rate examples: Example of Rate with Speed a dog travels 2 meters in 2 seconds; rate is 1 meter per second $$\text{taxa} = \dfrac{2~m}{2 ~s} = 1 m/s$$ Example of Rate with Telephone Tariff a telephone company charges R$ 1,00 per minute; rate is R$ 1,00 per minute $$\text{taxa} = \dfrac{R\\$~ 1,00}{1 ~\text{min} } = R\\$ ~1,00/ \text{min}$$