In 12 hours: 6 large pipes can drain 1 reservoir.
In 24 hours: 6 large pipes can drain 2 reservoirs.
In 24 hours: 3 large pipes can drain 1 reservoir. 
In 8 hours: 3 large + 9 small pipes can drain 1 reservoir.
In 24 hours: 3 large + 9 small pipes can drain 3 reservoirs.
But, by  we know that in those 24 hours 3 large pipes can drain 1 reservoir.
Therefore the other 2 reservoirs can be drained by the small pipes on their own:
In 24 hours: 9 small pipes can drain 2 reservoirs.
In 24 hours: 1 small pipe can drain 2/9 reservoirs.
In 216 hours: 1 small pipe can drain 2 reservoirs.
In 216 hours: 5 small pipes can drain 10 reservoirs.
Therefore 5 small pipes can drain 10 reservoirs in 216 hours.
216 hours ÷ 10 = 21.6 hours.
21.6 hours = 21 hours and 36 minutes.
The river Pregel runs through the town of Konigsburg. In the river are two islands, connected to each other and the rest of the city by seven bridges.
The students of Konigsburg often challenge each other to try to make a trip crossing all seven bridges exactly once - can you find the path they have to take in order to do this?
Direct Link: www.brainbashers.com?ZTNY
Hint: Try starting in one corner.
Answer: There is no such route.
This is a very famous mathematical problem which was first posed by Euler (pronounced 'oiler').
It was a founding problem in graph theory, an area of mathematics which is very important in modern times, and is used in everything from cryptography to route optimisations.