The cost of painting the total outside surface of a closed cylindrical oil tank as 50 paise per square decimatre is Rs. 198. The height of the tank is 6 times the radius of the base of the tank. Find the volume corredcted to 2 decimal places.
Given,
Height of tank = 6 × radius of tank
Let radius of tank = r decimeter
So, height of tank = 6r dm
Total surface area of tank = 
= 2πr(h+r) = 198×2
= 2πr(7r) = 396
= r2 = 
= r = 3 dm
Height = 6r = 6×3 = 18 dm
So, volume of tank = πr2h = 
9