Question

A dome of a building is in the form of a hemisphere from inside it was whitewashed at the cost of rupees 4989.60 if the cost of white washing is rupees 20 per meter square find the inside surface area of dome and volume of air inside the dome

Answer 1

Answer: $249.48\ m^2; 369.168\ m^3$

Step-by-step explanation:

Given

Cost of white-washing =Rs. 4989.60

Rate =20 per meter square

So, inside area of = $\dfrac{4989.60}{20}=249.48\ m^2$

The surface area of dome= $4\pi\ r^2=249.48$

$4\times 3.142\times r^2=249.48\\r^2=\frac{249.48}{4\times 3.142}=19.85\\r=4.455\ m$

The volume of air in the dome $V=\frac{4}{3}\pi r^3$

$V=\frac{4}{3}\cdot 3.142\cdot (4.45)^3\\V=369.17\ m^3$