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Yesterday, unaware of just how large a can of worms I was opening, I shared a graphic similar to the one above on Facebook, both on my personal profile and on the Zero To Cruising page. I then spent a considerable chunk of my day reading through the hundreds of comments, and trying to respond to many of them. As of this moment, people are still responding. What I found most amusing from this exercise is just how many people seem to be 100% sure of their answers, and yet are 100% wrong! Not only that, some people got very frustrated, and in a couple of cases, even seemed to get angry that someone was disagreeing with their beliefs. I noted that it was an interesting, if not unsettling, example of life in general. 


I don’t know the answer, so does that make me wise?

For the record, when I posted the puzzle, I did so noting that I didn’t believe there was enough information in the graphic to answer it definitively. And to tell the truth, I did so completely missing the fact that the passage from chamber 2 to 3 is blocked off. That shows just how observant I am!

Note: I don’t know if that passage was supposed to be blocked off or not, but it was on the image that I shared, so I’ll stick with that.

As far as the puzzle goes, my thinking is as follows:

  • Flow rate matters. If the flow rate into chamber 1 is greater than what can move through the passage into chamber 2, chamber 1 will fill first. Just yesterday I experienced this exact phenomena when I overfilled a funnel while topping up our outboard engine gas tank. Oops!

Many people argued that the diagram was supposed to be an accurate representation, and that the fluid was shown to be dripping, indicating a low rate of flow. OK, if that’s the case, I would counter by pointing out that we’re looking at a 2D drawing, and trying to guess volume. Which begs the questions:

  • Are the chambers cylindrical? If not, what is their depth? Are they all the same size (in the image I shared, we only care about chamber 1 and 2). If chamber 2 was significantly deeper than chamber 1, even at a very low rate of flow, chamber 1 would fill first. Or would it?
  • Are the passages between the chambers round? If so, what is their diameter? If to scale, and they are not round, what is their depth? Again, they could be microscopically thin, in which case, chamber 1 would fill first, even at a low flow rate.
  • Lastly, perhaps the fluid isn’t even water? Maybe it’s something much more viscous, which wouldn’t flow easily through the passages?

I have been told that there are countless places on the internet where people are arguing about this, and I’d rather this not become another one. It’s just a puzzle, and maybe I am overthinking it as I have been accused. I don’t really care. I’m sharing all this here for one reason only. That being, perhaps we shouldn’t be quite so sure of everything that we’re supposedly sure about. Keep an open mind, and don’t get upset if someone holds an opposing view point to you, especially to something that you see posted on the internet! 🙂


Question even this!

Lastly, if you do find yourself getting angry, about this puzzle, what I’ve written, or anything else for that matter, check out the great Spotify playlist shared by Rob Greenfield. We’ve been listening to it since yesterday and it’s excellent! Note that if you’re in some out of the way place like we are, you may need to use a VPN to access Spotify.


  1. Yup… just like everyone else (I assume!), I made assumptions. As you point out, the solution is indeterminate – the drawing does not provide enough information. A solution requires assumptions.

    I am embarrassed by my previous confidence.

  2. It’s the Dunning Kruger effect.

  3. I’ve seen this puzzle all over the internet.

    My view is the person(s) responsible for making it didn’t really have much a clue. No point in over-thinking it. It’s like a language puzzle made by somewhat clever 2nd graders with a 1500 word vocabulary.

    We can argue about what they meant, but at this point trying to reverse-engineer their original thoughts is about as easy as attempting to determine the shape of a hull by studying the wake it made in passing over 2 hours ago.

    • I’m sure there is an answer. Perhaps my pointing out all the undefined variables was my way of avoiding having to answer the puzzle in its most simple state? 🙂

      PS: I hate plumbing!

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