FINDING THE DIAMETER
To find the diameter given the circumference divide the circumference by π. D = C ÷ π
What is the biggest diameter of the circle you can bend out of 18 in. of wire?
Diameter = 18 ÷ π = 18 ÷ 3.14 = 5.729 inches
FINDING THE CIRCUMFERENCE
To find the circumference of a circle, multiply the diameter with pi. C = d ∙ π
This multiplication of course can be done the other way around as well: C = π ∙ d
Find the circumference of a hole with a diameter of 4.00 inches. Use π = 3.14
Circumference = d × π = 4 × 3.14 = 12.56 in
Using the circumference formula to find the diameter of a circle
When the circumference is known, it is possible to find the diameter of a circle
Check out the ADVANCED section. The exercises will further your understanding and help with building a bigger mental picture. It builds links between numbers and algebra. It is important to try alternative calculations or approaches, to sketch the shapes, label the shapes with the given numbers, tracking changes to units of measure, visualizing to cross-link the concepts of perimeter and numbers. We use the numbers from this sheet metal pipe example. If you spend 20 – 40 min working with the different ideas in the ADVANCED page, you`ll remember key formulas easier and you`ll learn new skills faster.