Question

The diameter of a circle is two times it’s radius. What equation shows another way to represent the area of a circle ?

Answer 1

 A = (πD^2)/4. d = diameter

Answer 2

Area of the circle can be written as:

$Area= \pi r^{2}$

Diameter is twice the radius, which means

Diameter = d = 2r
or
r = d/2

Using this value of r, we can write the equation for Area as:

$Area= \pi ( \frac{d}{2})^{2} \\ \\ Area= \frac{ \pi d^{2} }{4}$