• # 3 bulbs and 3 switches puzzle

Here we come up with another logical reasoning puzzle which was a very famous interview question a few years back.

There are three bulbs in a room and they are wired to three switches. The switches are outside the room. The room is locked. You have 30 seconds to determine which switch corresponds to which bulb. After 30 seconds, you can enter the room.

Simple na?
• Yes vijay, its simple. Just turn on the switch 1 and 2. Now turn off switch 2 and immediately go into the room. The bulb which is glowing corresponds to switch 1. The bulb which is diminishing its brightness corresponds to switch 2. And the third one which is not at all glowing corresponds to switch 3. Thats all.
Regards,
Rizwan.
Practice makes perfect..

• Hi Rizwan,

You are right. But the second bulb will diminish very quickly before you enter(Assuming room is locked, and you have to open the lock). Thus, I suggest, to touch the remaining two bulbs. The one which is hot corresponds to the second bulb. The one which is cold corresponds to the unpressed switch.

• Hi vijay,