How would you identify which switch corresponds to which light bulb, if you are only allowed one trip upstairs?
A man who lives on the tenth floor takes the elevator down to the first floor every morning and goes to work. In the evening, when he comes back; on a rainy day; or if there are other people in the elevator, he goes to his floor directly. Otherwise, he goes to the seventh floor and walks up three flights of stairs to his apartment.
Can you explain why?
Keep the first bulb switched on for a few minutes. It gets warm, right? So all you have to do then is … switch it off, switch another one on, walk into the room with bulbs, touch them and tell which one was switched on as the first one (the warm one) and the others can be easily identified …
Ball in a Hole – solution
All you have to do is pour some water into the pipe so that the ball swims up on the surface.
The Man in the Elevator – solution
The man is a of short stature. He can’t reach the upper elevator buttons, but he can ask people to push them for him. He can also push them with his umbrella.
~Steve~ H/T Brain Den