The speed of a railway engine is 42 Km per hour when no compartment is attached, and the reduction in speed is directly proportional to the square root of the number of compartments attached. If the speed of the train carried by this engine is 24 Km per hour when 9 compartments are attached, the maximum number of compartments that can be carried by the engine is :

P,Q and R are three consecutive odd natural numbers in the ascending order. Three times P is three less than two times R. The value of R is

A bag contains  Rs. 210 in one rupee, 50 np  and 25 np coins in the ratio of 2.5 : 3:4. What is the number of 50 np coins?