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Areas of Parallelograms and Trapezoids

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The formula for area is A=bh ... the end triangle off a parallelogram Move ... Draw 98 Drawing Areas of Parallelograms and Trapezoids PowerPoint ... – PowerPoint PPT presentation

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Title: Areas of Parallelograms and Trapezoids


1
Areas of Parallelograms and Trapezoids
2
  • A parallelogram has two sets of parallel lines.

3
  • The formula for area is Abh where b is the base
    and h is the height.
  • A(17)(12)204 ft2.

4
  • 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.

5
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.

6
Trapezoids
7
  • 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.

8
Circumference Area of a Circle
9
(No Transcript)
10
CIRCUMFERENCE
11
The circumference of a circle is
The distance around a circle
Hint Circumference remember circle around
12
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!
13
The diameter is the distance across a circle
through the center.
14
We use Pi as the measurement to help us find the
circumference of a circle.
Pi, not Pie!
15
HINT Pi 3.14
16
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.
17
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.
18
NOWLets have some fun.
Tell me what formula would be used to solve the
next five problems.
19
3in
C 2 x 3.14 x r
20
8ft
C 3.14 d
21
122mm
C 2 x 3.14 x d
22
17.5 cm
C 3.14 x d
23
122.5mm
C 2 x 3.14 x r
24
Now that we have determined the correct formula
for each, lets work the problems.
25
The answer is 18.8in
3in
C 2 x 3.14 x r
26
8ft
C 3.14 d
The answer is 25.1ft
27
122mm
C 2 x 3.14 x d
The answer is 766.2mm
28
17.5 cm
C 3.14 x d
The answer is 55cm
29
122.5mm
C 2 x 3.14 x r
The answer is 76,930mm
30
Classwork Homework
  • CW pg.550 1-16 evens pg.1-15 odds
  • WB pg. 84 85
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