# proportional

Two variable quantities are said to be proportional to one another if their quotient has a fixed value *m*. *m* is called the proportionality factor. For instance, the ratio of current to voltage is constant for a direct current (Ohm's law).

Two numbers are said to be **directly proportional** if they stand in direct ratio to one another, e.g. time worked and money earned (the longer the time worked the more money earned).

Two numbers are said to be **inversely proportional** if they stand in reciprocal (indirect) ration to one another, e.g. speed, and time taken to travel a certain distance at that speed (the greater the speed, the shorter the time taken).