3 switches, one lightbulb

Q.> You have a set of 3 light switches outside a closed door. One of them controls the light inside the room. With the door closed from outside the room, you can turn the light switches on or off as many times as you would like.

You can go into the room - one time only - to see the light. You cannot see the whether the light is on or off from outside the room, nor can you change the light switches while inside the room.

No one else is in the room to help you. The room has no windows.

Based on the information above, how would you determine which of the three light switches controls the light inside the room?

Answer:-

• You could turn on the first one for two minutes and turn it off. Then the middle for two minutes and turn it off. Then the last and run inside. If it is on then it is the last is it. If the bulb feels hot then the middle one. If only warm then the first.

• first any one of the switch and let it be on for 10 min and then close on the another switch and go inside the room if the bulb is lighted then the correct switch is 2 and if the bulb if not lighted but it is hot (feel it by touching) then it is the 1st switch otherwise the 3 rd switch