A tap, some pipes, seven containers… and a seemingly simple question: which one fills up first? This kind of puzzle is appealing because it requires less calculation than careful observation. Here, the key is to resist the urge to answer intuitively and follow the path of the water, as if you yourself were a drop ready to roll down the circuit.
The right approach: observe before concluding
When faced with the diagram, start with three golden reflexes:
Identify the obstacles: valves, plugs, pipes raised too high… all barriers invisible at first glance.
Read the slope of the circuit: the water obeys gravity and chooses the most direct and lowest path.
Comparing lengths: at the same flow rate, the shortest route almost always wins, especially if it has fewer turns and branches.
Keep in mind that, as long as a container is not filled to its outlet level (overflow), it acts as a dead end that does not feed the next part.
The classic trap: not all the pipes are “open”
The puzzle often hinges on minute details: a blocked section, an outlet located above the liquid level, a bend that rises too high. As a result, branches may seem promising but offer no passage. This is what confuses most people who answer too quickly.
