Question

Find the volume between the cylinders (it is a hollow cylinder). R= 12 cm, r= 9 cm. Height is 20 cm.

Answer 1

`\bf \textit{area of a circular ring}\\\\ A=\pi (R^2-r^2)\qquad \begin{cases} R=\textit{larger radius}\\ r=\textit{smaller radius}\\ --------\\ R=12\\ r=9 \end{cases}\implies A=\pi (144-81)`

volume of the hollow cylinder, the product of the area of the ring and the height of the cylinder