If the pipes A and B working with half of their efficiency can fill an empty cistern in 14 and 70 hours. Find the actual time in which working together they can fill the cistern with their full efficiencies.

5\(\frac{5}{6}\) h

⇒ A can do the work with half efficiency in = 14 h

⇒ A can do the work with full efficiency in = 7 h

⇒ B can do the work with half efficiency in = 70 h

⇒ B can do the work with full efficiency in = 35 h

A & B can do the work together in = \(\frac{35}{6}\) = 5\(\frac{5}{6}\) h