The ratio of efficiencies of two filling pipes is 4 : 5. There is a third emptying pipe which efficiency is two third of the average efficiency of first two filling pipes can empty a filled tank in 36 minutes. In how much time both the filling pipes can fill the tank when it is empty?
Correct Answer: 12 min
Explanation:
Let the efficiencies of filling pipes is 4p and 5p respectively.
Efficiency of pipe which empty the tank = 2/3 x 9p/2 = 3p
Total work = 3p x 36 = 108p
Time to fill the tank by both the pipes = 108p/9p = 12 min.
