# In this Section:

In this section, we learn how to calculate, write, and simplify ratios and rates. A ratio is a comparison of two quantities with the same units.
We use three methods to display a ratio: as a fraction, using the word “to”, or with a colon “:”. As an example, suppose a recipe calls for two cups of flour for every one cup of
sugar. The ratio of flour to sugar is said to be: 2:1. This is extremely useful if we wanted to double or triple the recipe. If we wanted to make three batches, we would multiply
each part by three and get six cups of flour and three cups of sugar. A rate is a ratio where the units are different. Most often we discuss “unit rates”, or the amount of one thing
per one unit of another. A good example is miles per gallon of gas. If a car can travel four hundred miles on ten gallons of gas, its fuel economy is 40 miles per gallon of gas. How
much of one thing (miles traveled), given a single unit of another (gallons of gasoline).