If quantity of good X demanded increases from 4000 units to 5000 units when price of good Y increases from Rs 75 to Rs 90, find Arc Cross elasticity of demand?
Two pipes P and Q can fill an empty tank in 25 hours and 20 hours respectively. Pipe R alone can empty the completely filled tank in 50 hours. Firstly both the pipes P and Q are opened and after 8 hours pipe R is also opened. What will be the total time (in hours) taken to completely fill the tank?