Areas of Parallelograms and Trapezoids

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Areas of Parallelograms and Trapezoids
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• A parallelogram has two sets of parallel lines.

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• The formula for area is Abh where b is the base
  and h is the height.
• A(17)(12)204 ft2.

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• To see the formula visually, cut the end triangle
  off a parallelogram
• Move the triangle to the other side
• The resulting rectangle has the same area as the
  parallelogram.
• To find the area of a rectangle multiply the base
  times the height.

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Trapezoids

• Trapezoids have one set of parallel lines and one
  set of lines that are not parallel.
• The parallel lines are the bases.
• The height is perpendicular between the bases.
• The slant heights may be the same or they may be
  different.

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Trapezoids
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• To see how the formula for area works, visualize
  two of the same trapezoids put together as shown.
  
• Notice a parallelogram with twice the area of the
  desired trapezoid.
• The area of the trapezoid is ½ the area of the
  parallelogram with height the same as that of the
  trapezoid, and a base that is the sum of the two
  bases of the trapezoid.

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Circumference Area of a Circle
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(No Transcript)
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CIRCUMFERENCE
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The circumference of a circle is
The distance around a circle
Hint Circumference remember circle around
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First we must define some things about a circle.
The radius is the distance from the center of a
circle to any point on a circle.
Hint I like to define it as halfway through!
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The diameter is the distance across a circle
through the center.
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We use Pi as the measurement to help us find the
circumference of a circle.
Pi, not Pie!
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HINT Pi 3.14
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Two formulas are used in finding the
circumference of a circle.
WHEN THE CIRCLE HAS A DIAMETER MEASUREMENT, USE
THE FOLLOWING FORMULA.
Circumference d
4in.
3.14 x 4in.
12.6in.
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When the radius of a circle is given, the
following formula should be used.
Circumference 2 r
2 x 3.14 x 5cm
31.4cm
HINT Always round your answers to the nearest
tenth.
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NOWLets have some fun.
Tell me what formula would be used to solve the
next five problems.
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3in
C 2 x 3.14 x r
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8ft
C 3.14 d
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122mm
C 2 x 3.14 x d
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17.5 cm
C 3.14 x d
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122.5mm
C 2 x 3.14 x r
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Now that we have determined the correct formula
for each, lets work the problems.
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The answer is 18.8in
3in
C 2 x 3.14 x r
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8ft
C 3.14 d
The answer is 25.1ft
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122mm
C 2 x 3.14 x d
The answer is 766.2mm
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17.5 cm
C 3.14 x d
The answer is 55cm
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122.5mm
C 2 x 3.14 x r
The answer is 76,930mm
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Classwork Homework

• CW pg.550 1-16 evens pg.1-15 odds
• WB pg. 84 85