How many cubic metres of earth must be dug out to sink a well which is

1.	How many cubic metres of earth must be dug out to sink a well which is 20 m deep and has a diameter of 7 metres? If the earth so dug out is spread over a rectangular plot 28 m by 11 m, what is the height of the platform so formed?
Answer» It is given in the question that, Diameter = 7m Hence, Radius = 3.5 m Depth = 20 m Volume of the earth to be dug out = \(\pi r^2h\) = \(\frac{22}{7}\times3.5\times3.5\times20\) = 770 m³ Volume of the earth piled upon the given plot = 28× 11 × h Therefore, Height = \(\frac{770}{28\times11}\) = \(\frac{70}{28}\) = 2.5 m

How many cubic metres of earth must be dug out to sink a well which is 20 m deep and has a diameter of 7 metres? If the earth so dug out is spread over a rectangular plot 28 m by 11 m, what is the height of the platform so formed?

Answer»

It is given in the question that,

Diameter = 7m

Hence,

Radius = 3.5 m

Depth = 20 m

Volume of the earth to be dug out = \(\pi r^2h\)

= \(\frac{22}{7}\times3.5\times3.5\times20\)

= 770 m³

Volume of the earth piled upon the given plot = 28× 11 × h

Therefore,

Height = \(\frac{770}{28\times11}\)

= \(\frac{70}{28}\)

= 2.5 m