Rate

From Wikipedia, the free encyclopedia

See also: rates (tax), naval rate, naval rating, or reaction rate.

A rate is a special kind of ratio, indicating a relationship between two measurements with different units, such as miles to gallons or cents to pounds. For example, suppose one spends 9 dollars on 2 pounds of candy. The rate $9 / 2 pounds compares the money spent to the number of pounds of candy.(or money)

The division operator, when dealing with rates, is sometimes expressed as "per". Also, if the units are expressed without abbreviation, the top unit is usually plural while the bottom is singular. For example, (5 meters)/(3 seconds) may be written as 5/3 meters per second.

Often rate is a synonym of rhythm or frequency, such as heart rate or sample rate.

A unit rate is a rate that is simplified so it has a denominator of 1. This type of rate is frequently used when referring to statistics.

[edit] Example

The civics membership in the U.S. House of Representatives is based on a population in the preceding census. In 1990, the population of the United States was about 248,000,000. There are 435 members in the house. On average, how many people are represented by each member of the house?

Write the rate that compares the population to the number of members of the house. Then divide both the numerator and the denominator by 435.

(248,000,000 people)/(435 members) ≈ (570,000 people)/(1 member).

This says that each representative represents about 570,000 people.