Title: Areas of Parallelograms and Trapezoids
1Areas 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.
5Trapezoids
- 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.
6Trapezoids
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.
8Circumference Area of a Circle
9(No Transcript)
10CIRCUMFERENCE
11The circumference of a circle is
The distance around a circle
Hint Circumference remember circle around
12First 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!
13The diameter is the distance across a circle
through the center.
14We use Pi as the measurement to help us find the
circumference of a circle.
Pi, not Pie!
15HINT Pi 3.14
16Two 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.
17When 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.
18NOWLets have some fun.
Tell me what formula would be used to solve the
next five problems.
193in
C 2 x 3.14 x r
208ft
C 3.14 d
21122mm
C 2 x 3.14 x d
2217.5 cm
C 3.14 x d
23122.5mm
C 2 x 3.14 x r
24Now that we have determined the correct formula
for each, lets work the problems.
25The answer is 18.8in
3in
C 2 x 3.14 x r
268ft
C 3.14 d
The answer is 25.1ft
27122mm
C 2 x 3.14 x d
The answer is 766.2mm
2817.5 cm
C 3.14 x d
The answer is 55cm
29122.5mm
C 2 x 3.14 x r
The answer is 76,930mm
30Classwork Homework
- CW pg.550 1-16 evens pg.1-15 odds
- WB pg. 84 85