Puzzle: there is one bulb inside the room and out the room these is 3 switches, you can go once out the room and on the any button and come in. After doing this process you have to tell which switch is the correct button for bulb?
Answer of puzzle:
suppose there is three buttons
button 1, button 2, and button 3.
Go out on the button 1 for 2-3 minutes. off the button 1 and on button 2 come in to the room.
Now of bulb is on it means button 2 is right switch because you on the button 1 for 2-3 minutes and that's why it hot.
otherwise check the bulb if its hot button 1 is right switch.
otherwise button 3 is right switch.