How many cubic metres of earth must be dug-out to sink a well 21 m deep and 6 m diameter?
The volume of the earth that must be dug out is similar to the volume of the cylinder which is equal to πr2h.
Height of the well =21 m
Diameter of the well= 6 m
∴ Volume of the earth that must be dug out = (π (32) (21)) m3= 594 m3