Greenwood press

QUADRILATERALS
95
A pantograph being used 
to magnify a picture of 
a dinosaur.
Parallelogram law for adding
vectors. The resultant vector
c =  a +  b is the diagonal of
the parallelogram. 

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online sources for future exploration
Demonstration of a pantograph

Floor plans




Home decorating

Maximize the area of a rectangular field with fixed perimeter

Surveying

Tessellation of quadrilaterals
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RATES
A rate describes change that is dependent on a variable, such as the change
of temperature in a month or the change in price of an item based on the quan-
tity sold. The concept of rate is studied throughout mathematics in different
forms. It can usually be identified in an expression by the word “per,” such as in
“two dollars per gallon”; or “for each,” as “one-half unit of credit earned towards
graduation for each required course completed”; or “for every,” as in “six points
for every touchdown scored.”
Rates are commonly associated with the amount of distance traveled, 
d, in
the equation 
d = rt, where r is the rate of an object and t is the amount of time
traveled. In this case, the rate would be expressed in units related to speed, such
as meters per second or miles per hour. Rate can also be used in contexts of pro-
duction levels for a given time period. For example, two hundred bushels of corn
are processed by the manufacturing plant each day, or twenty copies of the news-
paper are sold each hour at the newsstand. Rate is also associated with accumu-
lating or acquiring something, such as rainfall or a salary. For instance, the thun-
derstorm is producing rain at a rate of one inch per hour. At work, an employee
would use a rate to describe his hourly wage by saying that he earns $8 per hour
for delivering pizzas.