Question 11
A hotel porter mixes up 5 keys for 5 rooms. Each key opens exactly one room, and each room has one key. What is the smallest number of key-in-lock trials that is sufficient in the worst case to identify every key?
One trial means trying one key in one room lock. A remaining match may be inferred without trying it, and only identification is required, not physically opening all rooms. The source’s answer-only 24 is unresolved under its unspecified convention; this edition uses the explicit convention above.
One trial means trying one key in one room lock. A remaining match may be inferred without trying it, and only identification is required, not physically opening all rooms. The source’s answer-only 24 is unresolved under its unspecified convention; this edition uses the explicit convention above.