Finding the Diameter from the Area
(KS3, Year 7)
The LessonThe diameter of a circle is found from the area of a circle using the formula:
In this formula, A is the area of the circle. The image below shows what we mean by finding the diameter from the circumference:
How to Find the Diameter from the AreaFinding the diameter from the area is easy.
QuestionWhat is the diameter of the circle, with area 50 cm2, below?
Substitute the area into the formula. In our example, A = 50.
Diameter = √ (50⁄π) Diameter = √ (50 ÷ π) Diameter = √ (50 ÷ 3.14) Diameter = √ 16 cm Diameter = 4 cm
Answer:The diameter of the circle is 4 cm.
Lesson SlidesThe slider below shows another real example of how to find the diameter of a circle from the area. Open the slider in a new tab
Interactive WidgetHere is an interactive widget to help you learn about finding the diameter of a circle from its area.
Equivalent Formula for Finding the Diameter of a Circle from the AreaAn equivalent formula for how to find the diameter of a circle from the area is:
This is equivalent as the square root of 4 is 2.
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