Deep Thinking

# Try to solve this puzzle: Which cup will get filled first?

An interesting puzzle is going viral on social media at this moment. It seems pretty simple at first glance, but it’s actually a bit complicated, and allegedly 99% of people will get it wrong (at least on their first try). The question that you need to answer is: when you pour water into this specific setup of glasses and pipes, which glass will get filled all the way up first?

Take your time, think about it, and try to come up with an answer before checking the solution below!

#### Solution

You might not notice that the cups and pipes have several connector types at first glance. All the cups under the clogged pipes may be simply ruled out. Thus, the glasses with numbers 4, 5, and 6 are automatically eliminated from contention. Cup 7 has a hole in it rather than a stopped pipe. The cups above 7 would fill up more quickly in any situation where we could pour quickly enough to overwhelm the leak.

Thus, only options 1, 2, and 3 remain. However, cup 2 has the same illogical loop as cup 7, where a pour large enough to fill it would still fill cup 1 first despite its outflowing pipe. Otherwise, any normal pour would flow out the bottom so 7, and 2 would never fill.

That only leaves numbers 1 and 3. However, since 1 will never stop leaking water through cups 2 and 7, it will never be filled in this situation. Cup 3 is the only cup with a completely closed environment; both pipes leading outward are also close