Name given to certain ratios that generally include different kinds of quantities.

- A rate can be expressed in decimal notation, fractional notation, or as a percentage.
- A rate can express how one variable changes based on another one, as is the case for speed, where the distance covered depends on how much time has passed:
*d*= \(\frac{v}{t}\). - A rate can also be used to compare the real dimensions of one object to those of a model.
- It is acceptable to use the slash to write a rate, as in: 80 km/h or 12 L/100 km.

### Examples

- The birth rate corresponds to the number of births per 1000 inhabitants in a given region.
- The rate of increase in a salary is the percentage of increase in a salary per $100 of the current salary.
- The rate of variation in a stock market index expresses, in units of variation (percentage points), the increase or decrease of the value of a share or a group of shares between two observations.