Puzzle: Which tank gets filled first ? (no googling)

[left-of-center2012]

[samnsara]

1. 3?

[RandiFan1290]

2. 3

[CincyDem]

3. 5

[Zorro]

4. 3

[Cartoonist]

5. 4

lowest level opening

[Dem_4_Life]

6. 8

[blueinredohio]

7. 1

[jrthin]

8. 4

[flying_wahini]

9. 4

[physioex]

12. Ditto...EOM

[SCantiGOP]

22. yes it's 4

[Baitball Blogger]

38. It's 3. There's a clog in the line for 4.

[cemaphonic]

10. Gotta be 3, right?

[3catwoman3]

11. 4

eom

[angstlessk]

13. 6

OOPS, same problem as 4

[mercuryblues]

14. 4

[Locrian]

15. 3 (and only 3)

[Fla Dem]

43. Agree.

[BBG]

16. 4

[think4yourself]

17. 5

[Canoe52]

18. it's 3

[eppur_se_muova]

19. Tricky drawing. Most of the "drains" are blocked at one end or the other ...

easy to get it wrong if your eyesight is poor, but take your time and you conlcude it has to be 3 -- in fact, if the flow is low, *only* 3 will *ever* fill up.

[jberryhill]

20. 4, 5, 6 and 7 will never fill

Kinda obvious that people miss the lack of an opening between 3 and 4, and between 2 and 6; the lack of an outlet of the pipe into 5; and the hole in the bottom of 7.

You still have to make an unstated assumption about the flow rate from the faucet, the size of the pipes, and the viscosity of the fluid.

Assuming a non-viscous fluid, and a reasonably low flow rate from the faucet relative to the flow rate available through the pipes, then 3 fills first.

None of the others ever fill.

[SCantiGOP]

27. Not really an intelligence test

most people simply don't notice the blockages and hole in some tanks. So of course it is #3.

[jberryhill]

35. But if the tanks were all connected, it is an underdetermined problem

Since we don't know the flow rate, relative pipe size, and fluid viscosity.

I guess the assumption in that case would be a quasi-steady state filling with a non-viscous fluid, such that whenever the fluid level encounters a pipe, it goes through the pipe and does not continue to fill the vessel.

Given that it is underdetermined, then obviously there has to be a "trick" involved.

[sakabatou]

21. 3

[shraby]

23. 3

[SonofDonald]

24. Should be 3 n/t

[Sinistrous]

25. 5

on edit: oh rats.

[MuseRider]

26. 5

[hopeforchange2008]

28. 4

[underpants]

29. 3. There's no outlet.

[SeattleVet]

30. 3 is the only one that can be filled with this arrangement.

[awesomerwb1]

31. 3

[LonePirate]

32. Is the diagram drawn correctly to signify open and closed pipes/drains?

That makes a significant difference in the answer.

[petronius]

33. None of them - some greedy 1%er has rerouted the input to the faucet...

[jberryhill]

36. FTW!

The question is moot!

http://www.dailymotion.com/video/xewlks

[avebury]

37. 3

[Stuart G]

39. 7...wait..hole in 7, change my vote to 6,,oops ...4

[hunter]

40. None of them fill. There's no sides on any of the containers.

[yardwork]

41. 5

Whoops. Now I see it. Only 3.

[Fla Dem]

42. Its 3.

[benld74]

44. 4

[TexasBushwhacker]

45. 4

[Hamlette]

46. 3 and it's the only one that will fill because 7 has a hole in bottom

[Rollo]

47. Yes, it's #3

Water flows first out of the lower pipe on #1, into #3. There is a block in the line to #4, so as #3 fills, the pipe to #5 starts flowing, but there's a block in that line so #5 never gets any water. The pipe from #1 to #2 is higher than the pipe from #1 to #3, so #3 fills before #2, and #2 keeps on draining to #7 and then out the hole in the bottom of #7, so #2 never really fills (although the hole in #7 has no effect on the level in #2, it's just interesting).

Effectively #3 is has no outlet so it fills first.

[Rollo]

48. Call the plumber.

[Locrian]

49. I didn't cheat (see post 15), but did find this to "settle" the issue

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