13 thoughts on “Which cup fills first?

  1. The liquid would go to the bottoms of the recepticles (squares) first, before going into any of the thin tubes that go to the cups. The recepticle on the left qould be the first to fill to a tube leading to a cup, so #4 would fill first. This is how I make my coffee every morning, so I know.

  2. Way too many variables here to give a definitive answer. Obvious questions include the meaning of “closed off” paths like where 4 comes out of the tank, 9 exits into the cup, and 7 has in its path. Is it poor drafting of the layout (a common real life happening for engineers), or does it have meaning? Depending on the answer and whether it tells you the only cup with a remaining path (5), you also need to know about flow rates and pipe sizes and overall dimensions to know if tanks and pipes might overflow and cause “unintended” flows.
    I would also want to ask if there was some hidden reason why the odd cup numbering system was shown, perhaps indicating other invisible paths.
    Offhand, the only person to fail the “Academy Test” was the one who designed the question!

  3. None. The amount in the carafe will fill most of the apparatus before any of it reaches the tube to 5. Even if some did manage to flow to 5, that cup still won’t be filled.

  4. Wow … I wish I was as immediately observant as the others here! I figured the answer was 4 – but then someone pointed out that 4 is blocked at the tank. So, then I picked 7 – but a poster noted that there’s no continuity at the corner of the tube, so of course I chose 9 – but then someone noticed that the end of that tube isn’t open! So – then I felt the only possible answer is 5 … until Scott said that maybe there isn’t enough fluid in the pot to fill any of the cups! So the correct answer is … no one wins … sigh.
    Thanks for the challenge, Jonco!

  5. The tube feeding 4 and 9 is lower than the one feeding 5 and 7. So no liquid will flow into the latter until the former is filled. Since the line feeding 4 is blocked, only 9 will receive any coffee. Coffee will flow out of 9 until the pot is empty.

    If the entire pot is rapidly poured, 9 will still fill-up first. Depending on how much coffee is in the pot, some may make it to 5.


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