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Locks and keys so any three of five can open

Question

Five people share a safe. They want any group of 33 or more of them to be able to open it, but no group of 22 or fewer. The safe gets several locks, all of which must be opened; each lock may have several copies of its key, but a key fits only its own lock. What is the minimum number of locks, and how many keys does each person carry?

Short answer

1010 locks; 66 keys each. Every pair must be shut out by some lock whose keys they both lack, and that lock's keys must be held by all three others; distinct pairs need distinct locks, giving (52)=10\binom52=10 locks with 33 keys each. The 3030 keys spread evenly, 66 per person.

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