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

Answers (1)

Solution:  We have ,

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

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

Area of the inner curved surface

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

$\therefore$ Cost of plastering the inner curved surface $= Rs (495\times 3)=Rs1485$

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