The socks puzzle is a deceptively simple logic puzzle, one that'll trick the overthinker, and have others go "That's it?". The puzzle, which comes in many different forms, is as follows:
You're going to a fancy dress party, but as you're getting dressed there's a blackout in your home, and there are no other light sources in sight. You decide to simply dress in the dark. You manage to dress yourself almost completely (well done), but you're now faced with putting on socks in the dark. You know you only have 2 kinds of socks: black socks, and blue socks. But without light you can't tell which is which.
How many socks do you have to grab before you can guarantee you have a pair of the same color?
Those of you part of the "That's it?" group will already see the answer straight away. Others might be overthinking it, and might read too much into the purposely slightly misleading question at the end. If you're thinking you have to grab two socks, which have to be the same, or if you're thinking you have to remove a given amount of socks to make sure only two of the same are left, or any other similar trail of thought, then you're definitely part of the overthinkers.
The answer is simple, you only have to grab 3 socks to have a guaranteed pair. The only possibilities are black and blue. So with 3 socks you'll either have 3 black socks, 3 blue socks, 2 black socks plus a blue sock, or 2 blue socks plus a black sock. No matter what there will be at least 2 socks of the same color in those three you grabbed.
This puzzle is easy to adapt to an RPG setting too, you could replace the socks with power orbs for example, and make the party carry the smallest amount of orbs, while still holding two of the same, to a power switch for the door at the end of the dark corridor.
Of course in the sock version the puzzle doesn't explain how you'd actually put on the right two socks in the dark after grabbing three of them. But let's be honest, if the guests at a fancy dress party can't appreciate the clearly more stylistic choice of putting on two different socks, then perhaps that party isn't all that fancy after all, haha.