|A) 16 min||B) 12 min|
|C) 14 min||D) 20 min|
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.