Question 9
My father’s vault is protected with a code that can only be unlocked by entering a three-digit combination password, with each digit being either 1, 2 or 3.
The vault will only be opened if the buttons corresponding to the three digits of the password are pressed in succession. For example, anyone can press 1, 2, 3, 1, 2 and the vault will unlock if the password happens to be 312.
My mother doesn’t know the password of the vault, but she wants to open it. What is the minimum number of buttons that she must press to be sure that the vault will be opened? Note that the vault does not have an [ENTER] button.
The vault will only be opened if the buttons corresponding to the three digits of the password are pressed in succession. For example, anyone can press 1, 2, 3, 1, 2 and the vault will unlock if the password happens to be 312.
My mother doesn’t know the password of the vault, but she wants to open it. What is the minimum number of buttons that she must press to be sure that the vault will be opened? Note that the vault does not have an [ENTER] button.