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In this activity, we will solve problems using the circumference and area of circles.
You will need a calculator for this!
Recap the formulae we need:
Circumference of a circle = 2 x π Radius
in short we write
C = 2 π r
Area of a circle = π x Radius x Radius
in short we write
A= π r2
We are going to answer some mixed questions using these formulae.
Example
A circular, gold-coloured badge has a radius of 10 mm.
What area of metal is needed to make this badge?
Answer rounded to 1 decimal place.
Answer
π is usually taken to be 3.142, but your calculator should have the π button on it which will make your calculations more accurate.
Area = π r2
A = π x 102
A = π x 100
A = 314.2 mm2 (1 dp)
Let's do some questions now!
