This Coffee Riddle Going Viral On Twitter Will Break Your Uncaffeinated Brain

Everyone loves a good brainteaser, right? Well, maybe not… and especially not before having your morning coffee. But what about having your brainteasers and your coffee at the same time? That’s actually the name of the game this time round — but even so, it turns out that this viral coffee brainteaser currently making the rounds on Twitter is just too much for the internet’s collective, uncaffeinated brain.

The puzzle was posted by Twitter user @_herbeautyxo on Nov. 9, although I’ve been unable to determine whether that’s the first time it’s ever appeared online or not. (I’m guessing it’s not, but it’s definitely responsible for the brainteaser’s current popularity, so at least there’s that.) It presents with an image of a network of pipes and reservoirs leading to four different mugs numbered 4, 9, 5, and 7. Above the whole system of pipes and mugs is a disembodied hand holding a Chemex coffee maker filled with java. The hand is pouring the Chemex’s contents into a reservoir at the top of the pipe system. The question is this: Which mug will the coffee reach first?

Twitter users have been responding to the original tweet with their answers… with varying degrees of success. So: Which mug is it? Do you know?

Is It… Mug 4?


How About Mug 9?

Also nope.

Mug 9, Followed By Mug 5?

Wrong again.

This Sequence, In Order?

Still wrong.

What About This?

You’re going to hate the actual answer so much.



Here’s How To Solve It:

First, look at the section of Mug 4’s pipe that joins upwith the little reservoir separating it and Mug 9.

Then, look at the end of Mug 9’s pipe.

Now, look at the section of Mug 7’s pipe where it bends at aright angle.

All three of these pipes are physically sealed off from the mugs to which they lead.

That means that the answer to this puzzle isn’t a matter of figuring out the rate at which the coffee travels through the pipes, the rate at which each reservoir will fill up, or anything else that involves math or physics. It’s a matter of examining the image closely enough to notice the most important details. Those details reveal that only one mug actually gets any coffee from this network of pipes: Mug 5.

It’s worth noting, though, that this answer also assumes that the amount of coffee being poured from that fancy Chemex is enough to fill up pretty much the entire pipe system — or that the supply of coffee is never-ending, as this Twitter user points out:

That’s the funny thing with brainteasers: Although the answer to the actual puzzle might be logical, the setup of the problem often doesn’t follow real world logic at all.

Remember how I said that I wasn’t totally sure when this puzzle first made its way to the internet? That’s true for this particular version of it — but other versions have been traversing the web for quite some time. A similar puzzle asking which of 12 water tanks would fill up first went viral on WhatsApp and Facebook during the summer of 2017, although as Quora user Stewart Bible pointed out, this one isn’t a terribly well-constructed puzzle: The answer is “supposed” to be tank F, but ultimately, there isn’t enough information to say for certain which tank will fill first.

Here’s yet another version of this same puzzle:

And another:

And another, which has the same setup as the coffee puzzle,just with a different cup — the one on the far right — being the one that’s actually capable of being filled up

Interestingly, that last video was posted on Oct. 26 of this year, meaning it predates the Twitter version by about two weeks.

I would bet money that the puzzle itself is actually ancient (possibly literally) — which means that it’ll likely pop up again in the future to stump further generations, too. Funny how we never seem to lose interest in these kinds of things, isn’t it?