Question

what is the diameter of a circle with an area of 78.5 squared cm

Answer 1

Given:

The area of the circle = 78.5 squared cm​

We know that:

$\text{Area}=\pi\cdot r^2$

so,

$\begin{gathered} \pi\cdot r^2=78.5 \\ \\ r^2=\frac{78.5}{\pi}=\frac{78.5}{3.14}=25 \\ \\ r=\sqrt[]{25}=5 \end{gathered}$

so, the radius of the circle = r = 5 cm

The diameter of the circle is two times the radius

So, the answer will be Diameter = 2 * 5 = 10 cm