Question

Acistern is filled in 5 hours and it takes 6 hours when thereis a leak in its bottom. If the cistern is full, in what time shall the leak empty it?

• A. 6 hrs
• B. 5 hrs
• C. 30 hrs
• D. 15 hrs

Answer 1

Answer: (C)

30 hrs

Answer 2

For the capacity of cistern Take LCM of 5,6 = 30

Efficiency to fill the cistern = $\frac{30}{5}$ $\frac{units}{hr}$

= 6 $\frac{units}{hr}$

Assume the efficiency of leak = $- x \frac{units}{hr}$

From the question, $(6 - x) × 6 = 30$

$6 - x = 5$

$x = 1$

From above, time taken by leak to empty it = $\frac{30}{1} hrs$

The correct option is (C): 30 hrs