# Geometry ```Geometry: Perimeter
Formulas
Rectangle:
P = 2l + 2w
Triangle:
P=a+b+c
Parallelogram:
Square: P = 4s
Trapezoid:
P = c + b1 + b 2 + d
P = 2c + 2b
Regular shapes have sides with equal lengths.
Find the perimeter:
Rectangle
Square
Triangle
11
4
6
3
2
4
P = 2l + 2w
P = 4s
P = 2( 11 ) + 2( 4 )
P = 4(
P = 22 + 8
P = 30 units
)
2
Find the perimeter: Trapezoid
7
5
4.5
Parallelogram
4
3
8
If two sides of an isosceles triangle
are 6 in and the third side is 8 in,
find the perimeter.
The length of a rectangular park is 55 yd.
The width is 47 yd. How many yards of
fencing are needed to surround the
park?
3
Geometry: Area &amp; Circles
Formulas
Rectangle:
P = 2l + 2w
A = lw
Triangle:
P=a+b+c
A = &frac12; bh
Parallelogram:
Square: P = 4s
A = s2
Trapezoid:
P = c + b1 + b 2 + d
A = &frac12; (b1 + b2)h
P = 2c + 2b
A = bh
Find the Area.
14 ft
5
c
m
9
cm
6 ft
7 1/3 in
A = lw
A = s2
A = ( 14 )( 6 )
A=(
A=
)2
A = 84 sq. ft
11 yd
2
6.4
yd
m
4m
15.3 yd
A=
A=
4
The height of a trapezoid is 5 in.
The base measures 16 in. and 18 in.
Find the area of the trapezoid.
The length of the base of a parallelogram
is 6 &frac12; in. and the height is 10 &frac14; in. Find
the area of the parallelogram.
5
Circles: Circumference &amp; Area
The diameter, which goes through the center of the circle, is twice the length of the radius.
Circumference is the distance around the “edge” of the circle. C = 2πr
Circumference is very similar to perimeter.
Area is all the “space” inside the circle.
A = π r2
π is a Greek letter pronounced as pie, and is an irrational number (there is no end to the
numbers behind the decimal and no pattern to those numbers).
22
We use numbers like 3.14 and
as an approximation for to calculate answers.
7
π
The length from the center
to the edge of the circle.
Circumference
Diameter
The length from one edge of the circle
to the opposite edge through the center.
Area
6
Find the Circumference and Area of each circle.
5
3.4 ft
2
C = 2πr
C = 2 ( 3.14 )( 5 )
C = 31. 4 units
A = π r2
A = ( 3. 14)( 5 )2
A = ( 3.14 )(25)
A = 78.5 sq units
6
m
11
```