# Rate

## Rate

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.