top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

How can you determine with which of the three switches the light bulb can be switched on?

+5 votes
813 views

A light bulb is hanging in a room. Outside of the room, there are three switches, of which only one is connected to the lamp. In the starting situation, all switches are 'off' and the bulb is not lit.If it is allowed to check in the room only once to see if the bulb is lit or not (this is not visible from the outside), how can you determine with which of the three switches the light bulb can be switched on?

posted Apr 27, 2014 by anonymous

Share this puzzle
Facebook Share Button Twitter Share Button LinkedIn Share Button

1 Answer

+1 vote

Step 1. Switch on any bulb for 1 min lets say first one.
Step 2. Switch on the second bulb and go inside. there will be three cases :

case 1. If bulb is on then second switch is correct one.
case 2. If bulb is off then touch bulb it if it is hot then first one was the correct switch.
case 3. if both above cases are not true then third one the right switch.

answer Apr 28, 2014 by Amit Kumar Pandey



Similar Puzzles
0 votes

You are standing in front of a room with one light bulb inside of it.
You can not see if it is on or off.
Outside the room there are three switches in the off positions.
You may turn the switches any way you want to.
You stop turning the switches, enter the room and know which switch controls the light bulb. how?

0 votes

There are 3 switches downstairs, each corresponding to one of the light bulbs upstairs.
How can you figure out which light switch goes to which light bulb by only making 1 trip upstairs?

0 votes

On a circle there are 2014 light bulbs, 2 are ON, and 2012 are OFF. You can choose any bulb and change the neighbor's state from ON to OFF or from OFF to ON. Doing so, can we get all 2014 light bulbs on ? If yes, How?

0 votes

A one armed surgeon with a hand wound needs to operate on three patients. The surgeon only has two gloves.
How can he operate on the three patients without risking exchange of fluids? (Remember he only has one arm so he only needs to wear one glove at a time.)

+1 vote

Ravi has three boxes with fruits in his barn: one box with apples, one box with pears, and one box with both apples and pears. The boxes have labels that describe the contents, but none of these labels is on the right box.How can Ravi determine what each of the boxes contains, by taking only one piece of fruit from one box?

...