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MathNet 2016-part-07 — 182 problems (EN–VI) Question 126

Math Olympiad Vault · MathNet 2016-part-07 — 182 problems (EN–VI)

Question 126

Chris and Paul each rent a different room of a hotel from rooms $1$-$60$. However, the hotel manager mistakes them for one person and gives "Chris Paul" a room with Chris's and Paul's room concatenated. For example, if Chris had $15$ and Paul had $9$, "Chris Paul" has $159$. If there are $360$ rooms in the hotel, what is the probability that "Chris Paul" has a valid room?