Turn on a lightbulb - Solution
You turn two switches ‘on’ and one switch ‘off’ and you wait…
Just before entering the room you turn one switch from ‘on’ to ‘off’.
If the lightbulb is warm, but off, it has to be that last switch.
If it is on, it has to be the switch that is turned on.
If it cold and is off, it has to be the switch which was already off.
Peter Hosszu has sent an excellent update on this riddle:
‘I think you could have four switches (let’s name them A, B, C and D) instead of three.
The solution in this case:
Turn on A and B for a while, then turn off A and turn on C.
The switch in control depending on the state of the bulb:
A warm and dark
B warm and light
C cold and light
D cold and dark.’
Maybe now you could help these ladies with their light.
I’d just turn them all on
I’d just turn them all on I mean the lightbulb will still be on right?
its so easy to do this …. the easiest solution is ………. USE A TORCH !
Something about the answer is incorrect.
“You turn two switches ‘on’ and one switch ‘off’ and you wait…”
This defeats the conclusion.
You turn ONE switch on and wait.
Before entering the room turn it off and turn another one on.
Therefore if switches are A, B and C:
A on
B off
C off
Before entering the room:
A off
B off
C on
If the bulb is warm (off): A
If the bulb is cold (off): B
If the bulb is on: C
but what if the light was on to begin with…. then it doesn’t work.