Question

How many cubic metres of earth must be dug out to sink a well 22.5 m deep and of diameter 7m? also find the cost of plastering the inner curved surface at Rs 3 per square metre.

Answer 1

Hello...
Answer..

Volume of earth to be dug out = Volume of the well.

$= \frac{22}{7} \times \frac{7}{2} \times \frac{7}{2} \times {22.5 \: m \: }^{3} = {866.25 \: m \: }^{3}$

Area of the inner curved surface =2πrh


$= 2 \times \frac{22}{7} \times \frac{7}{2} \times {22.5 \: m \: }^{2} = {495 \: m \: }^{2}$

Cost of plastering the inner curved surface Rs


$= Rs \: (495 \times 3) = Rs \: 1485.$


Hope it helped ☺☺☺

Answer 2

Hiiii.....

Volume of earth to be dug out = Volume of the well.

22/7 X 7/2 X 7/2. X 22.5 m^3=866m^3

Area of the inner curved surface =2πrh


2 X 22/7 X 7/2 X 22.5 m ^2=495 m^2

Cost of plastering the inner curved surface Rs


= Rs (495 X 3) = Rs 1485.


Hope it helped