Properties of Proportions

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Properties of Proportions
11.1
RECIPROCAL PROPERTY If two ratios are equal,
their reciprocals are also equal. CROSS PRODUCT
PROPERTY

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Example 1
Use the cross product property to solve the
proportions. Check for extraneous solutions.
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Example 2
Use the cross product property to solve the
proportion. Check for extraneous solutions.
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Example 3
Use the cross product property to solve the
proportion. Check for extraneous solutions.
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Example 4
Two rectangles are similar with a scale factor of
73. If the smaller rectangle has a perimeter of
60 centimeters, what is the perimeter of the
larger rectangle?
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Example 5
To estimate the number W of blue whales in a
portion of the Indian Ocean, researchers marked
200 different whales. Months later the
researchers checked 300 whales in the area and
found only 15 that were marked. Write and solve
a proportion to estimate the whale population in
that portion of the Indian Ocean.
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Example 6
The Chief Crazy Horse Memorial is being carved
from Thunderhead
Mountain in South Dakota. When completed, it
will be the worlds largest stone sculpture 641
feet wide and 563 feet high. The ratio of the
sculpture of Chief Crazy Horse to actual size is
140 to 1.
a. Estimate the diameter of the horses nostril
in the sculpture. Assume the diameter of a
horses nostril is 3 inches.
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b. Estimate the length of Chief Crazy Horses
index finger in the sculpture. (Assume that the
average length for a mans index finger is 3 ½
inches.)
c. Estimate the distance around Chief Crazy
Horses neck if it is 2240 inches around in the
sculpture.
Homework
p. 646 18-40e, 47, 48, 60-64e