Need math help to Answer These Questions about the volume of a cone

A right triangle with sides 3 cm, 4 cm and 5 cm is rotated the side of 3 cm to form a cone. The volume of the cone so formed is:2. In a shower, 5 cm of rain falls. The volume of water that falls on 1.5 hectares of ground is:3. A hall is 15 m long and 12 m broad. If the sum of the areas of the floorand the ceiling is equal to the sum of the areas of four walls, thevolume of the hall is: