Post on 26-Mar-2015
5th GradeMiss Cameron’s Class
The circumference of a circle is
The distance around a circle
Hint: Circumference remember circle around. Circumference is a circle’s perimeter.
The diameter is the distance across a circle through the
center.
Vocabulary.
The radius is the distance from the center of a circle to any point on a
circle.
Hint: It is ½ the diameter
We use Pi as the measurement to help us find the circumference of a circle.
Pi, not Pie!
Two formulas are used in finding the circumference of a
circle.
Circumference = d 3.14 x 4in.
12.6in.
WHEN THE CIRCLE HAS A DIAMETER MEASUREMENT, USE THE FOLLOWING FORMULA.
4in.
Circumference = 2r
When the radius of a circle is given, the following formula
should be used.
2 x 5cm x 3.14
31.4cm
HINT: You may round to the nearest tenth
NOW…Let’s have some fun.
Tell me what formula would be used to solve the next five problems.
3in
C = 2 x r x 3.14
8ft
C = 3.14 d
122mm
C = 2 x r x 3.14
17.5 cm
C = 3.14 x d
122.5mm
C = 2 x r x 3.14
Now that we have determined the correct
formula for each, let’s work the problems.
3in
C = 2 x 3.14 x r
The answer is: 18.8in
8ft
C = 3.14 d
The answer is: 25.1ft
122mm
C = 2 x 3.14 x d
The answer is: 766.2mm
17.5 cm
C = 3.14 x d
The answer is: 55cm
122.5mm
C = 2 x 3.14 x r
The answer is: 76,930mm
r ²6 m
Another formula
• ½ d x
12 ft
Find area
9 ft
Find area
15 mm
13 cm
Find area
19 ft
Circles rapBy Miss Cameron
Circles, those tricky circles! Pow!
I said those circles.Those tricky circles!
Pow!
Circumference is perimeter; it’s all the same
They just try to trick you with a name game.
Circumference is diameter, the length across
Multiplied by pi
So don’t get lost
Pi is 3.14, a funny number.
Rap with me now, & please don’t slumber.
Area for a circle is radius squared.
So half the diameter and make it squared.
Well you know what to do, so do it now.
Find circumference and area of a circle. POW!
Circles, those tricky circles. POW!
I said those circles, those tricky circles. POW!