A water tank has two holes. The 1st hole alone makes the tank empty in 3 min and 2nd hole alone makes the tank empty in 5 min. If water leaks out at a constant rate, how long in minutes does it take if both the holes together empty the tank?
A factory buys 7 machines. 2 MachineA, 4 MachineB and rest MachineC. Prices of the machines are Rs 56000, Rs 45000 and Rs 30000 respectively. Calculate the average cost of these machines.