Coffee puzzle leaves Twitter totally stumped – which cup would be filled up first?

Daily Mail ^ | 10 November 2017 | Bianca London

[mairdie]

Brainteaser shows a funnel of coffee being poured into different pipes

Poster asked her followers to guess which cup received coffee first

People were left stumped by the confusing brainteaser on social media

[Arm_Bears]

5

[Gay State Conservative]

As does #7!

[mairdie]

Best explanation yet.

[Hillarys Gate Cult]

I was able to solve the Towers of Hanoi math puzzle in one move. A B-52 airstrike.

[xp38]

5 because all the others are blocked. # 9 at the last opening

[Mercat]

9 is blocked too.

[exDemMom]

Bah, I didn’t notice that the pipe to 9 is also blocked. So 5 will fill up, but only after that large reservoir is filled. I’m assuming airflow is unimpeded as the coffee pours in—although the diameter of the pipes could prevent air from escaping, in which case the coffee will fill the first reservoir and proceed to run all over the floor.

[mairdie]

I’m up for a cup of coffee with 5 splenda and an inch and a half of cream. What are you guys inspired for?

[ctdonath2]

#5.

4,9,&7 are blocked.

Scary that it took 24 posts before someone got it right.

[Alberta's Child]

Seems clear that it's #9, unless I'm missing something. But you really need to know the flow rate for the coffee and a lot of the physical characteristics of the pipes, chambers and the coffee itself to know for sure.

This is actually similar to a problem I had on my P.E. exam some years ago. LOL.

[mairdie]

My first husband was a high energy physicist and on his PhD exam at the University of Chicago they asked how you could tell how fast the boat was going on Lake Michigan if you couldn’t see land.

[Fresh Wind]

The Beatles had the answer back in 1968 knowing that the question would be asked in 2017.

[Alberta's Child]

#5 is the only one that doesn’t have a blocked pipe.

[HangnJudge]

5
All other paths are blocked

[exDemMom]

Yes, I noticed that after I posted.

So my revised answer is either cup 5 or the floor. The diameters of the pipes may be small enough to prevent the air to escape in the opposite direction, which would cause the coffee to spill as soon as the first reservoir is filled.

[piroque]

#5 will fill first , as #4 #7 #9 the pipes are blocked off

[Alberta's Child]

I'd be curious to know how that question would be answered. I could figure out how to do a rough measurement, but I'm sure it's wrong for a PhD exam where they're probably expecting some precision.

I just got this problem wrong on my first try, too. LOL.

[radmanptn]

This is a stupid puzzle; it’s obvious that none of those cups would fill up. After all why use some Rube Goldberg contraption when you could just drink the coffee straight from the pot?

[mairdie]

Interestingly enough, Chicago DIDN’T expect precision. What they taught was thinking, not calculation. Try your rough approach. I’ll bet you’ll be right.

Another example of a question on a sociology test was that the Queen of England is visiting the university and all the men’s urinals are turned off. Is this an example of deference or demeanor?

Probably one of the reasons he was my FIRST husband, was that we used to fall asleep playing mental chess, or him setting me square roots to solve to two decimal places. I got really good at that. We married for five years from when I was 19. Pure luck to marry a really good man that young.

[WildHighlander57]

#9 because #4 is blocked, and the pipe leading to #5 & #7 is higher than the one leading to #9.