Three pipe P, Q and R can fill a tank in 12 minutes, 18 minutesand 24 minutes respectively. The pipe R is closed 12 minutesbefore the tank is filled. In what time the tank is full?
The volume of a right circular cone, whose radius of the base is same as one-third of its altitude, and the volume of a sphere are equal. The ratio of the radius of the cone to the radius of the sphere is :