C can empty it in 60 hours .Pipes A and B were Kept open simultaneously for 12 hours . when person reached the tank when it should have been full , he obeserved the pipe c also remained open by mistake for these 12 hours .He immediately closed it . In what time will the tank get full after C is closed
Pipes A and B together can fill the tank in 12 hours and C alone can empty the tank in 60 hours.Â
So, part of tank emptied by pipe C in 12 hours = $$\frac{12}{60} = \frac{1}{5}$$
Now, this $$\frac{1}{5}^{th}$$ part of the tank will be filled by pipes A and B together in $$\frac{1}{5} * 12 = 2.4$$ hours