# One Bulb with 3 Switches

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You have 3 switches in a room. One of them is for a bulb in next room. You can not see whether the bulb is on or off, until you enter the room. What is the minimum number of times you need to go in to the room to determine which switch corresponds to the bulb in next room.

ronret45 Expert Asked on 30th July 2015 in

we have to go to that room only once.

Steps:
First switch on the first switch, keep it on for say 2-3 minutes.
then switch of first switch and on the second switch.
as soon as u on the second switch go to the room.

If you found that the bulb is glowing  that means the second switch corresponds to the room.
if not then touch the bulb if it is warm that means it corresponds to the second switch if not then it corresponds to the third switch.

ronit12 Scholar Answered on 30th July 2015.

Minimum visit=1 and Maximum vist=2

On Switch A and check (visit one )

if bulb is on then Switch a is bulb switch if not

Turn off A and turn on B, go to room and check (second visit)

if bulb is on the switch B is bulb switch , else switch C

Sajan Curious Answered on 2nd September 2016.

Minimum visit=1 and Maximum vist=2

On Switch A and check (visit one )

if bulb is on then Switch a is bulb switch if not

Turn off A and turn on B, go to room and check (second visit)

if bulb is on the switch B is bulb switch , else switch C

Sajan Curious Answered on 2nd September 2016.

1 just get good at guessing nerd or just flick all the switches on

Distinguishedeagle Starter Answered on 12th November 2019.

here is the details:

S1,S2,S3

Switch ON all 3 switches one by one. dont visit the room as bulb will be glowing for sure.
Then,  Switch OFF S3, check bulb on or off, If OFF, then Minimum visit=1;
else
Switch OFF S2 leaving S3 in OFF, check bulb on or off, If OFF, then  visit=2;
else
Then,  Switch OFF S1 leaving S3,S2 off, check bulb on or off, If OFF, then  visit=3;

\Hence ,
Minimum visit=1 and maximum vist=3

Pruthiraj Swain Starter Answered on 8th January 2016.

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