A hemispherical bowl with diameter 14 cm has to be painted inside and outside. How much it will be charged at the rate of ₹20 per 40 cm² ?

The radius of a cylinder is doubled due to which the volume of the new cylinder also gets doubled. The height of the new cylinder is what percentage of the old cylinder?

The volume of the hemisphere is 486∏ cm². If the radius is tripled, then what will be its curved surface area (in cm²)?