Lesson 18 — Activity 4: Measuring the Area of a Circle
Completion requirements
Lesson 18 — Activity 4:
Measuring the Area of a Circle
The area of a circle is the measurement of the surface area inside the circle.
The formula is written as follows.
A = 3.14 × r × r
You will remember that pi (3.14) was used to find circumference, too.
Below is an example of how to find the area of a circle.
Remember: The radius of a circle is the straight line from the centre to the circumference (the outer part of the circle).
Click on the Play button below to watch a video on how to find the circumference and area of a circle.
Self-check!
Try This!
Using your calculator, try answering the questions below on your own first. When you have finished, click on the tab below to check your answers!
A putting green has a radius from the
cup
to the outer edge of the green of 15 feet. What area is covered by the putting green?
Kenya's ferret likes to go outside on a leash. If the leash that is 4 metres long is tied to a peg in the lawn, what is the area of the
yard
that his ferret can cover?
A medium pizza has a radius of 12 inches in
diameter, while a large pizza has a radius of 18 inches. Cole likes pizza! Would he get more by buying two medium pizzas or one large pizza? Round to the nearest whole number for each answer.
Area of the putting green: 3.14 x 15 x 15 = 706.5 ft squared
Area of the
yard: 3.14 x 4 x 4 = 50.24 m squared
Two medium pizzas = 3.14 x 12 x 12 = 452 (x two pizzas) = 904 in squared OR
One large pizza = 3.14 x 18 x 18 = 1,017 in squared.
Therefore, Cole would get more if he bought one large pizza!
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