How to find the diameter when area of a circle is given?

In previous lesson, the concept of finding the radius when area of a circle  given was explored. In this presentation, we’ll explain how to find the diameter of a circle when its area is given.

As already explained in previous lessons that the diameter is the line across a circle through its center. A diameter is the longest chord of the circle and it is twice as long as the radius of the circle.

In previous post we calculated the radius of a circle, when its area was given and you already know that the radius times 2 is the diameter.

Hence, you can just find the radius when the area of a circle is given and then multiply your result by 2 to get the diameter.

Example on finding the diameter of a circle from its area

For example; consider the area of the circle is given to be 40 square inches and we need to find its diameter.

To solve the above problem, we can find the radius of this circle from its area using the formula, as shown below:

Area of the circle “A” = 40 square inches

Consider “r” is the radius of the circle, so we can replace the above area symbol “A” by the formula to find the area of a circle; which is "pi times radius squared", as shown in the next step

Hence the diameter of a circle with area equal to 40 square cm is found to be 7.14 cm.

Some teachers may use the direct formula to find the area of a circle using diameter, but the above method is more common and easier.