Question

7. How many cubic metre of soil must be dug out to sink a well which is 21 m deep and has a diameter of 8 m?
If the soil so dug out is spread over a rectangular plot 24 m * 11 m, what is the height of the platform formed?
8.​

Answer 1

Radius of well =4m

height of well=21m

$volume \: of \: earth \: dug \: out = \\ \frac{1}{3} \pi \: {r}^{2} h \\ = \binom{1}{3} \times \binom{22} {7} \times {4}^{2} \times 21 {m}^{3} \\ \\ = 352m ^{3}$

height of platform =Volume of well÷area of plot

$\frac{352}{14 \times 11} \\ = 2.28m$