A stone is thrown into still water and the figure below represents the concentric circular phenomenon known as ripple effect. The radius of the first circle is \(9\ cm\). If the radius of each subsequent circle is \(5\ cm\) more than the previous. Which circle has a radius of \(74\ cm\)
 
concentric circles.png
The \(^{th}\) circle has a radius of \(74\ cm\).