U6L1
Perimeter & Circumference
• 9-1 Determine the perimeter of a composite figure.
• 10-1 Solve problems involving circumference.
Perimeter
• Perimeter- the distance around a polygon
• Polygon- a closed plane figure formed by 3 or more line segments
that intersect only at their endpoints (vertices)
• To find the perimeter P of a polygon, you add the lengths of its
sides.
Perimeter Practice
P=3+7+3+7
P = 20
Perimeter Practice
P=1+5+4+2+7
P = 19
Perimeter Formulas
• Square
• P = 4S
• Rectangle
• P = 2L + 2W
• Triangle
• P=a+b+c
• Ormie the Pig
Circumference
• Circumference = the distance around a circle
• Radius = a line segment with one endpoint at the center of a
circle and the other endpoint on the circle
• Diameter = a line segment that passes through the center of a
circle and has endpoints on the circle
Formula
• r = radius
• d = diameter
A radius is ½ of a diameter
A Diameter is 2 radii (plural of radius)
What is Pi?
Pi = the ratio of circumference of a
circle to length of its diameter
Circumference Practice
• Which formula do we use?
• Why?
C = dπ
C = 4π
Circumference Practice
• Which formula do we use?
• Why?
C = 2π r
C = 2π3
C = 6π
Assignment
P. 456 – 457 #7-10, 17-28
• Day 1 – do only Perimeter problems (Wednesday, 2/13)
• Day 2- do circumference problems (Thursday 2/14)