6 . A right circular cone has base radius 9 cm and its height is 36 cm. A section is made by a plane parallel to its base through a height of one third the height of the cone. Find the volume of the sectioned part.
8 . A, B and C start to walk together from the same place round a circular path of length 15 km. A walks at the rate of 5 km/hr, B at the rate of 3 km/hr and C, at the rate of $5\over 2$ km/hr. They will meet at the starting place at the end of-