Question

How many cubic meters of earth must be dug out to sink a well 7 m deep and radius 5 m? Find the cost of plastering its lateral surface area at the rate of 15 per metre cube

Answer 1

first of all mate,the question must be 15 per metre square as area is measured in square units
height of the well=7m
radius of the well=5m
volume of the earth to be dug out=volume of the well
=
$\pi \times {r}^{2} \times h$
=
$\frac{22}{7} \times 25 \times 7$
=
$550 {m}^{3}$
lateral surface area of the well=
$2 \times \pi \times r \times h$
=
$2 \times \frac{22}{7} \times5 \times 7$

=
$220 {m}^{2}$
total cost of plastering the well= Rs 220 X 15
=Rs 3300