A pump can fill a tank with water in 3 hours. Because of a leak, it took $3 \frac{1}{3}$ hours to fill the tank. In how many hours can the leak alone drain all the water of the tank when it is full?

30

A + = 3hrs, A + B = \( {3 }_{3 }^{1 } \)hrs = \(\frac{10}{3}\) hrs,

⇒ A + B = 9,   (Efficiency)

⇒ 10 + B = 9,

⇒ B = -1,

⇒ Time required by B to empty the full cistern alone = \(\frac{30}{1}\) = 30 hrs.