6 th Grade SPI: 0606.4.4 Calculate with circumferences and areas of circles.
Mar 27, 2015
6th Grade
SPI: 0606.4.4 Calculate with circumferences and areas of circles.
The circumference of a circle is
The distance around a circle
Hint: Circumference remember circle around
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!
The diameter is the distance across a circle through the
center.
We use Pi as the measurement to help us find the circumference of a circle.
Pi, not Pie!
HINT: Pi =3.14
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 = 2 r
When the radius of a circle is given, the following formula
should be used.
2 x 3.14 x 5cm
31.4cm
HINT: Always round your answers 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 3.14 x r
8ft
C = 3.14 d
122mm
C = 2 x 3.14 x d
17.5 cm
C = 3.14 x d
122.5mm
C = 2 x 3.14 x r
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