The area of a circle is directly
proportional to the square of its
radius. a circle with a radius of 2
cm has an area of 12.566 cm^2.
what is the radius of a circle with
an area of 78.54 cm^2?
[? ] cm
round to the nearest whole number.

Step-by-step explanation:

Let r be the radius of the circle and A be the area of the circle.

Given:

And

The area of a circle is directly  proportional to the square of its  radius.

A ∝

-----------(1)

Where k is the constant of proportionality

Find constant value by substituting

in equation 1.

Find by substituting k and value in equation 1.

where: 25.004 ≅ 25

Therefore; the radius of the circle is 5 cm.