Suppose you're in a group of 200 people in a room. Everyone is handed out a random unique dominion card (yes they just bought DA).
In the next room, someone put another copy of the same 200 dominion cards in 200 envelopes, one in each.
Now one by one, a person is selected to go to the next room. In that room, he's allowed to look in 100 enveloppes. His task is to find the enveloppe containing his own card.
After looking at cards in enveloppes, this person will always put the cards back, leave the room in exactly the same state as it was before he came in, and leave the scene through the back door. No communication back to the group is allowed whatsoever.
You win if everyone in the group finds his own card. Your goal is to make a plan that maximizes this chance.
You are allowed to make a plan for all of the 200 people before the first one starts, and everyone else will do whatever you suggest. In this plan, you can assume some order on the enveloppes, so your instructions could include something like "open up the first enveloppe", "open up enveloppe 32 - 132" or "open up the first enveloppe, and if it's a card that costs $4 or more continue with enveloppe 67".
The solution has a theoretical upper limit of 50% because the first person has a 50% chance of failing no matter what you come up with. If everyone has a chance of 50%, your total score would only be 0.0000000000000000000000000000000000000000000000000000000000062%, rather disappointing. How high can you go?