A tap takes 8 seconds to fill a jar and 6 minutes to fill a.drum. Rahul has to fill the drum with the jar. First he fills the jar and then brings it to the drum and pours the water into the drum. The time taken to bring the jar from the tap to the drum is 10 seconds. Unfortunately, the jar develops a leak, which can empty the full jar in 40 seconds. What will be the minimum total time required by Rahul to fill the drum?

Let the capacity of Jar and Drum is 8 and 360 respectively. 

Quantity of water filled in Jar in 1 second = 1

It takes 40 seconds by the hole to empty the Jar completely. 

So. effective time taken to fill the jar = $$\frac{1}{\frac{1}{8} - \frac{1}{40}}$$ = 10 seconds.

It takes 10 seconds to bring the Jar to the drum. So, quantity of water in Jar emptied in 10 seconds = $$8 * \frac{10}{40} = 2$$

Quantity of water poured into Drum by Jar = 6 

Total time taken to pour this 6 unit of water = Time taken to fill the Jar + Time taken to bring the Jar to the Drum = 10 + 10 = 20 seconds

Number of time Jar is used to fill the drum = $$\frac{Capacity of drum}{Quanttiy of water filled by jar in one go} = \frac{360}{6} = 60 times$$

Total time taken to fill the drum = 60 * 20 = 1200 seconds = 20 minutes