Lesson 17 — Activity 1: Measuring Circumference
Completion requirements
Lesson 17 — Activity 1: Measuring Circumference
You may remember from L9 — A1 that circumference is the distance (or perimeter) around a circle.
The perimeter around a circle is called the circumference.
The circumference of a circle is calculated by using special formulas.
Remember:
π (pi) is a symbol from the Greek alphabet pronounced "pie" and has a value of 3.14.
d is the
diameter, which is
the distance through the middle of a circle from one side to the other.
r is the
radius, which is the distance from the centre of a circle to anywhere on the outside edge.
To find the circumference of a circle, use the following formula:
C = πd
Circumference = π x
diameter
Pi
has a
constant
value
that is approximately 3.14.
C = πd
Circumference = π x diameter
Pi has a constant value that is approximately 3.14.
So what about the other formula?
Will it give us the same answer?
Let's look again at the example above. The diameter of the circle was 100 m. To find the radius, you take HALF of the diameter (half of 100 m is 50 m).
So in the example above, the formula would be:
C = 2 x 3.14 x 50 = 314 m
The answers are the same!
Let's take a look at two more examples of how to use each of the formulas!
Let's take a look at two more examples of how to use each of the formulas!