Greenwood press

RATES
101
A maximum value of a quad-
ratic function can be found
by locating the horizontal
tangent line.

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Gross national product data

Motion


Motion of a piston

Occupational health and safety

Pipe flow

Roofing

Slope use permit

Stressed out: slope as a rate of change

Universal currency converter


Exchange rates for world currencies

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RATIO
A ratio is a quotient of two numbers. One of the most famous ratios in math-
ematics is 
π ≈ 3.14159, the ratio of circumference of a circle to the diameter. A
ratio is different from a rate, in that the units for the numerator and denominator
in a ratio are the same. A ratio does not have any units of measurement, unlike
rates that have units such as miles per hour or dollars per pound. Some examples
of ratios that are given here are really rates, but it is common practice in partic-
ular occupations and sciences to call them ratios.
There are many statistics dealing with money that are ratios. The federal gov-
ernment maintains the Consumer Price Index (CPI) and Cost of Living Index
(COL). The CPI is the ratio of costs of common items in the current year to the
costs of the same items during 1982–1984. The costs are usually expressed as a
multiple of 100, so that the number represents the current cost of purchasing
goods and services that would have cost $100 during 1982–1984. In 2001, the