Question

How many cubic metres of earth must be dug to sink a well 21m deep and 6m diameter​

Answer 1

$\sf{Volume \: of \: well = Volume \: of \: earth \: dug \: out}$

Well is in the form of Cylinder. Therefore, we can use the formula of volume of Cylinder.

$\texttt { \underline{\fbox{Volume of cylinder = \green{πr²h }}}}$

$\sf{Volume \: of \: well = \frac{22}{ \cancel7} \times 3 \times \cancel{21}}$

$\sf{Volume \: of \: well = 22 \times 3 \times 3}$

$\textsf { \pink{ \underline{ \underline{ \fcolorbox{blue}{pink}{Volume of well = 198}}}}}$