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Perimeter
is the word used to describe the distance around the outside
of a figure.
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Triangle |
3
sides |
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Quadrilateral |
4
sides |
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Pentagon |
5
sides |
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Hexagon |
6
sides |
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Heptagon or Septagon |
7
sides |
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Octagon |
8
sides |
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Nonagon |
9
sides |
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Decagon |
10
sides |
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Dodecagon |
12
sides |
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Refresh your polygon
memories:
When working with perimeter, references may be made to
the names of polygons. Listed
at the left are some of the more common polygons whose names you should know.
Remember that "regular
polygons" are polygons whose sides are all the same length
and whose angles are all the same size. Not all polygons are
"regular".
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Circumference
is the word used to describe the distance around the outside of a
circle.
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Like perimeter, the
circumference is the distance round the outside of
the figure. Unlike perimeter, in a circle
there are no straight segments to measure, so a
special formula is needed.
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|
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Use
when you know the radius.
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Use
when you know the diameter. |
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Example 1:
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Ed and Carol
are jogging around a circular track in the park. The
diameter of the track is 0.8 miles. Find, to the nearest
mile, the number of miles they jogged if they made two complete
trips around the track. |
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= (3.141592654)(0.8) = 2.513274123 miles (one
trip)
2(2.513274123) = 5.026548246 = 5 miles
This problem is shown being done
with full calculator (TI-83+/84+) entries.
Work should be held in the calculator until the final rounding of the
answer occurs.
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Example 2:
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For an art
project at school, you need a piece of string long enough to wrap
around the outer edge of this starfish. What is the shortest
possible length for the string? |
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Perimeter = 2 +
1.5 + 1 + 2 + 1.5 + 2 + 2 + 3 + 2.5 + 2
= 19.5 inches |
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