The cost of fuel in running an engine is proportional to the square of speed in km/h and is Rs. 64 per hour when the speed is 16 km/h. Other cost amount is 100 per hour. Find speed which would minimize the cost.

Q. The fuel charges for running a train are proportional to the square of the speed generated in km per hour, and the cost is Rs $48$ at $16$km per hour. If the fixed charges amount to Rs.$300$ per hour, the most economical speed is

Q. The fuel charges for running a train are proportional to the squre of the speed generated in miles per hour and costs $Rs.48$ per hour at $16$miles per hour. What is the most economical speed if the fixed charges i.e. salaries etc. amount to $Rs.300$ per hour.

Q. When travelling x km/hour, a truck burns diesel at the rate of $\frac{1}{300}(\frac{900}{x}+x)$ litres per km. If the diesel oil costs $40$p.per litre and driver is paid $Rs.1.50$ per hour, find the steady speed that will minimize the total cost of the trip of $500$ km.

Q. 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 compartment attached. If the speed of the train carried by this engine is 24 km per hour when 9 compartments are attached , what is the maximum number of compartments that can be carried by engine ?

Q. The speed of railway engine is 42 km per hour when no compartment is attached, and the reduction in speed is directly proportional to 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: