9.14 The lock opens only if a specific three-digit number is entered. An attempt consists of randomly selecting three digits from the five given. The number was guessed only on the last of all attempts. How many attempts preceded the successful one?
9.14 I method. The first digit could be chosen in five ways, the second also in five ways, i.e., for a two-digit number there were $5^{2}$ options. Thus, the total number of three-digit numbers under these conditions was $5^{3}=125$, and 124 unsuccessful attempts preceded the successful one.

II method. The total number of attempts is equal to the number of arrangements with repetitions of five elements taken three at a time, i.e., $\widetilde{A}_{5}^{3}=5^{3}=125$. Therefore, the number of unsuccessful attempts is 124.

Answer: 124 attempts.