Riddles

henryzz · 2017-08-01, 12:46

A riddle came up at lunch.

There are two rooms. One has a light bulb and the other has three light switches in it.

You start in the room with the switches and can only go through the door once. How can you work out which switch turns the light bulb on?

Nothing can be dismantled and you can't see though the door.

science_man_88 · 2017-08-01, 13:02

Quote:

Originally Posted by henryzz

A riddle came up at lunch.

There are two rooms. One has a light bulb and the other has three light switches in it.

You start in the room with the switches and can only go through the door once. How can you work out which switch turns the light bulb on?

Nothing can be dismantled and you can't see though the door.

find the ones that work the fans and light in the room you are in eliminate them leaving one left that has to be the light of the other room.

henryzz · 2017-08-01, 13:20

Quote:

Originally Posted by science_man_88

find the ones that work the fans and light in the room you are in eliminate them leaving one left that has to be the light of the other room.

The other two switches do nothing.

davar55 · 2017-08-01, 13:28

Quote:

Originally Posted by henryzz

...and can only go through the door once....

Can you go outside and check through the window?

science_man_88 · 2017-08-01, 13:32

Quote:

Originally Posted by henryzz

The other two switches do nothing.

can you see under the door ?

thyw · 2017-08-01, 14:01

There must be a trick to it, maybe the switches?
All possible cases for the switches:

leaving all of them off
turning on 1
turning on 2
turning on all

Just thinking: Case 1-4 are the opposite, with them we can confirm that the switches do something.With case 2 if the light isn't on, then we have a 50% (sub)chance to guess the right one from the remaining ones if it's on, if it's on we have found it (33% in total), with case 3 is the opposite of case 2.
So:
It's similar to [STRIKE]that 3 door thing show where they show the wrong door[/STRIKE] Monty Hall problem .

Batalov · 2017-08-01, 14:48

Quote:

Originally Posted by henryzz

You start in the room with the switches and can only go through the door once.

Open the door, but don't go. Check all switches one by one. ^_^

It's a riddle, not a problem, - don't expect there to be a logical solution.

rogue · 2017-08-01, 15:12

Most people assume that the door is either closed or cannot be opened.

petrw1 · 2017-08-01, 15:29

1. Turn on light switch 1 and wait for 3 minutes (or so)
2. Turn it off and turn on light switch 2 and immediately enter the room.
3. If the light is off it is switch 3.
4. If it is on:
- and the bulb is cool it is switch 2.
- and the bulb is warm it was switch 1.

This solution assumes you can get close enough to the bulb to touch it.

R. Gerbicz · 2017-08-01, 15:48

Right, then solve it for 3 bulbs!
Each bulb has exactly one switch, you need to find the switch for each bulb.

axn · 2017-08-01, 16:06

Quote:

Originally Posted by R. Gerbicz

Right, then solve it for 3 bulbs!
Each bulb has exactly one switch, you need to find the switch for each bulb.

Same setup. Each bulb will be in a different state (hot/off, on, cold/off)

2017-08-01, 12:46	#1
henryzz Just call me Henry "David" Sep 2007 Cambridge (GMT/BST) 2³·3·5·7² Posts	Riddles A riddle came up at lunch. There are two rooms. One has a light bulb and the other has three light switches in it. You start in the room with the switches and can only go through the door once. How can you work out which switch turns the light bulb on? Nothing can be dismantled and you can't see though the door.

2017-08-01, 14:01	#6
thyw Feb 2016 ! North_America 83 Posts	There must be a trick to it, maybe the switches? All possible cases for the switches: leaving all of them off turning on 1 turning on 2 turning on all Just thinking: Case 1-4 are the opposite, with them we can confirm that the switches do something.With case 2 if the light isn't on, then we have a 50% (sub)chance to guess the right one from the remaining ones if it's on, if it's on we have found it (33% in total), with case 3 is the opposite of case 2. So: It's similar to [STRIKE]that 3 door thing show where they show the wrong door[/STRIKE] Monty Hall problem . Last fiddled with by thyw on 2017-08-01 at 14:03

2017-08-01, 15:29	#9
petrw1 1976 Toyota Corona years forever! "Wayne" Nov 2006 Saskatchewan, Canada 1001001000100₂ Posts	Solution I THINK .... spoiler alert. 1. Turn on light switch 1 and wait for 3 minutes (or so) 2. Turn it off and turn on light switch 2 and immediately enter the room. 3. If the light is off it is switch 3. 4. If it is on: - and the bulb is cool it is switch 2. - and the bulb is warm it was switch 1. This solution assumes you can get close enough to the bulb to touch it.

2017-08-01, 15:48	#10
R. Gerbicz "Robert Gerbicz" Oct 2005 Hungary 2²×7×53 Posts	Right, then solve it for 3 bulbs! Each bulb has exactly one switch, you need to find the switch for each bulb. Last fiddled with by R. Gerbicz on 2017-08-01 at 15:51

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2017-08-01, 15:12	#8
rogue "Mark" Apr 2003 Between here and the 18CB₁₆ Posts	Most people assume that the door is either closed or cannot be opened.