Riddles, brain puzzles and mathematical problems

**Bridge** · 12-08-2012, 02:00 PM

(12-08-2012, 01:29 AM)Chronofox Wrote: still nope

It's obvious my probability needs work. In any case, I looked over it again and came up with:

0.0274 (successful non-Swedish applicants) / 0.29272 (all successful applicants) = 9.36%

Is this correct?

**Froge** · 12-08-2012, 11:34 PM

yep you go next

**Bridge** · 12-08-2012, 11:58 PM

Light bulb

There is a room that contains one light bulb. Just outside the room there are three light switches, but only one of them is connected to the light bulb inside of the room (the other two don't do anything). You are allowed to set the switches in whatever position you like (they only have two states - on and off) and you can then enter the room. Note that you may only enter the room once (opening the door counts as entering it) and you cannot peak through the keyhole or any other opening. Find out which of the switches controls the light bulb.

**Froge** · 12-09-2012, 12:19 AM

Does the bulb start off light or dark?

Edit: nevermind

**Bridge** · 12-09-2012, 12:36 AM

(12-09-2012, 12:19 AM)Chronofox Wrote: Does the bulb start off light or dark?

Edit: nevermind

Yeah, it starts off dark and you have to determine which one turns it on.

**Froge** · 12-09-2012, 12:56 AM

Can this puzzle even be solved?

Case 1: All switches off. The room is dark. The one that controls the bulb could be any of the three.
Case 2: Turn on one switch. If the room is light, then that switch must be the correct one. If the room is dark, it's either of the other two.
Case 3: Turn on two switches. If the room is dark, then the last switch must be the correct one. If the room is light, then the correct switch must be either of the two you just turned on.
Case 4: Turn on all switches. The room is light. The one that controls the bulb could be any of the three.

Cases 1 and 4 as well as 2 and 3 are reflections of each other (in terms of light/dark). 1 and 4 are useless, while cases 2 and 3 gives you a half chance of guessing the correct switch if it is dark or light respectively. Because we can't enter the room twice, I don't see how the puzzle could be solved.

**Bridge** · 12-09-2012, 01:04 AM

(12-09-2012, 12:56 AM)Chronofox Wrote: Can this puzzle even be solved?

Case 1: All switches off. The room is dark. The one that controls the bulb could be any of the three.
Case 2: Turn on one switch. If the room is light, then that switch must be the correct one. If the room is dark, it's either of the other two.
Case 3: Turn on two switches. If the room is dark, then the last switch must be the correct one. If the room is light, then the correct switch must be either of the two you just turned on.
Case 4: Turn on all switches. The room is light. The one that controls the bulb could be any of the three.

Cases 1 and 4 as well as 2 and 3 are reflections of each other (in terms of light/dark). 1 and 4 are useless, while cases 2 and 3 gives you a half chance of guessing the correct switch if it is dark or light respectively. Because we can't enter the room twice, I don't see how the puzzle could be solved.

I couldn't solve it either, but if you apply some lateral thinking it is possible. The solution is actually quite ingenious.

**Froge** · 12-09-2012, 01:05 AM

dammit Bridge

there goes my sleep tonight

**Bridge** · 12-09-2012, 01:07 AM

(12-09-2012, 01:05 AM)Chronofox Wrote: dammit Bridge

there goes my sleep tonight

Have fun.

**BAndrew** · 12-09-2012, 03:09 AM

(12-08-2012, 11:58 PM)Bridge Wrote: Light bulb

There is a room that contains one light bulb. Just outside the room there are three light switches, but only one of them is connected to the light bulb inside of the room (the other two don't do anything). You are allowed to set the switches in whatever position you like (they only have two states - on and off) and you can then enter the room. Note that you may only enter the room once (opening the door counts as entering it) and you cannot peak through the keyhole or any other opening. Find out which of the switches controls the light bulb.

If this puzzle is solveable that means that there is a way to measure the temperature of the light bulb (so you know if it was open or not). It has to do something with that, otherwise the riddle is not solveable.