Question

How much fabric is required to cover x buttons in the shape of a circle whose radius is 3x ?

Answer 1

Radius of 1 button = r = 3x

Fabric required to cover 1 button = Area of the circle

= $\pi r^{2}$

= $\pi (3x)^{2}$

= $9\pi x^{2}$

Total number of buttons = x

Fabric required to cover 1 button = $9\pi x^{2}$  

Fabric required to cover x buttons = $x(9\pi x^{2} )$

$=9\pi x^{3}$

Hence, fabric required to cover x buttons $=9\pi x^{3}$  sq. units