You have 7 doors, each with a sign on it. Each sign says a different number of keys. You can open any door with the number of keys on the sign. But, there's a catch! One of the doors is locked with no keyhole, and one of the doors has an infinite number of keys on its sign. Which doors do you open?
Door 1: 1 key
Door 2: 2 keys
Door 3: 3 keys
Door 4: ∞ keys
Door 5: 1 key
Door 6: 6 keys
Door 7: 7 keys
Open Door 4 (Infinite Keys) Open Door 1 (1 Key) Open Door 2 (2 Keys) Open Door 5 (1 Key) Open Door 6 (6 Keys) Open Door 7 (7 Keys)Which door will open, and which will not? Ah, it depends on the number of keys you have... or not.