# Post your puzzles/brain-teasers here



## Audi Driver P.E. (Mar 7, 2019)

The only rule, you must personally know the answer before you post your puzzle. I'll start:


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## NikR_PE (Mar 7, 2019)

Audi driver said:


> The only rule, you must personally know the answer before you post your puzzle. I'll start:




[D]


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## Audi Driver P.E. (Mar 7, 2019)

NikR said:


> [D]


Sorry, incorrect.


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## aog (Mar 11, 2019)

E - assuming that the side view shown is the elevation of the right side of the front view.


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## Audi Driver P.E. (Mar 11, 2019)

aog said:


> E - assuming that the side view shown is the elevation of the right side of the front view.


It can be assumed that it is. E is incorrect however.


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## NikR_PE (Mar 11, 2019)

Audi driver said:


> Sorry, incorrect.


Do i get a second chance? 

because if not D, it G


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## Audi Driver P.E. (Mar 11, 2019)

NikR said:


> Do i get a second chance?
> 
> because if not D, it G


If you're going to guess, you should at least supply rationale.


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## wilheldp_PE (Mar 11, 2019)

Reading comprehension is a bitch.  I was trying to figure out which top view was the correct one, but the puzzle description says which top view cannot be correct.  I was about to post something about there not being enough information to solve it because you aren't told which side of the top view is the front and which is the side.  That makes this harder than I'm willing to solve.


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## Audi Driver P.E. (Mar 11, 2019)

wilheldp_PE said:


> Reading comprehension is a bitch.  I was trying to figure out which top view was the correct one, but the puzzle description says which top view cannot be correct.  I was about to post something about there not being enough information to solve it because you aren't told which side of the top view is the front and which is the side.  That makes this harder than I'm willing to solve.


There is enough information and the solution is rather easy, actually.


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## NikR_PE (Mar 11, 2019)

wilheldp_PE said:


> Reading comprehension is a bitch.  I was trying to figure out which top view was the correct one, but the puzzle description says which top view cannot be correct.  I was about to post something about there not being enough information to solve it because you aren't told which side of the top view is the front and which is the side.  That makes this harder than I'm willing to solve.


I guess I need to read better.


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## leggo PE (Mar 11, 2019)

Maybe I'm over- or under-thinking it, but I don't even see how the front and side views go together if the blocks are each either completely transparent or solid black.

I mean, wouldn't you see a black block through a transparent block, if the transparent block was in front of the black one?

Ignoring that, I don't see a single choice that even works with the front and side views shown. So I'd say all of the options don't work.


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## DoctorWho-PE (Mar 11, 2019)

I agree with Leggo, I don't see how any of the options work.

EDIT:  I have revised my opinion.  See below.


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## Dexman PE PMP (Mar 11, 2019)

I'm making the assumption that the top, front and side views can be combined to form an isometric cube like this, with the front on the left side, side on the right and top on top:






If the transparent blocks are genuinely clear, you can see through all clear blocks to the first black cube, even if it's 4 deep. In that case, the full cube would be mostly clear blocks with only a dozen or so black blocks scattered throughout. Without rotating the face or side views, only answers A &amp; G satisfy the top two rows of both face &amp; sides. Reverse engineering through the options, Answer A works.


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## wilheldp_PE (Mar 12, 2019)

Dexman PE PMP said:


> only answers A &amp; G satisfy the top two rows of both face &amp; sides. Reverse engineering through the options, Answer A works.


That's the solution that I reached, too, before going back and reading the question.  You are supposed to choose the solution that DOESN'T work, not the one that does.  I think that all but one of the answers works if you rotate your perspective.


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## aog (Mar 12, 2019)

I stand by my answer based on the bottom left square in arrangement E - shouldn't it be clear?


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## leggo PE (Mar 12, 2019)

Calling @Audi driver, P.E..


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## Audi Driver P.E. (Mar 13, 2019)

leggo PE said:


> Maybe I'm over- or under-thinking it, but I don't even see how the front and side views go together if the blocks are each either completely transparent or solid black.
> 
> I mean, wouldn't you see a black block through a transparent block, if the transparent block was in front of the black one?
> 
> Ignoring that, I don't see a single choice that even works with the front and side views shown. So I'd say all of the options don't work.


Yes, that is exactly how it works.


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## Audi Driver P.E. (Mar 13, 2019)

aog said:


> I stand by my answer based on the bottom left square in arrangement E - shouldn't it be clear?


Solution E is an incorrect answer. Bottom left square may be black.
 

Note that I have verified the answer using a SolidWorks model.


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## Audi Driver P.E. (Mar 13, 2019)

Dexman PE PMP said:


> I'm making the assumption that the top, front and side views can be combined to form an isometric cube like this, with the front on the left side, side on the right and top on top:
> 
> 
> 
> ...


Answer A does indeed work and is therefore not correct.


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## Audi Driver P.E. (Mar 13, 2019)

Here is the only clue I will give. You can assume this is true. And if you do, you may have to rotate some of the various top views proffered to see if they work.


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## leggo PE (Mar 13, 2019)

Audi driver said:


> Yes, that is exactly how it works.


Woohoo @vhab49_PE, you see that?? K, back to the drawing board.


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## aog (Mar 13, 2019)

I think there's more than one answer


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## DoctorWho-PE (Mar 14, 2019)

F


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## Audi Driver P.E. (Mar 15, 2019)

aog said:


> I think there's more than one answer


Only one answer does not work.


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## Audi Driver P.E. (Mar 15, 2019)

vhab49_PE said:


> F


Sorry incorrect.


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## aog (Mar 15, 2019)

Audi driver said:


> you may have to rotate some of the various top views proffered to see if they work﻿.


I missed this before...now I agree that E can be a correct solution.  I say that G cannot work because the center block of the top view would need to be clear to be correct.


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## Audi Driver P.E. (Mar 15, 2019)

aog said:


> I missed this before...now I agree that E can be a correct solution.  I say that G cannot work because the center block of the top view would need to be clear to be correct.
> 
> View attachment 12683


Winner winner chicken dinner!  How to know that the center block must be clear?   Front view would require that the black block be in row 1 and/or 3 and not in 2, 4, or 5. Side view requires that it be in row 2 and/or 4 and not in row 1, 3, or 5. These things are incompatible. (note: no rotation of the top view required to ascertain this)


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## JHW 3d (Mar 26, 2019)

Just seeing this now. I was scrolling down thinking I hope no other asshole guesses G so I can be King Asshole. 

Damnit. 

G all day long people. 

(Ok there you go, I’m the asshole)


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## Audi Driver P.E. (Dec 12, 2019)

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?


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## BabaYaga (Dec 17, 2019)

what about changing the wiring, or does the room has window?  :eyebrows:


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## Audi Driver P.E. (Dec 17, 2019)

BabaYaga said:


> what about changing the wiring, or does the room has window?  :eyebrows:


No and no.


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## Orchid PE (Dec 17, 2019)

Do we have all the information we need to answer the question?


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## NikR_PE (Dec 17, 2019)

Audi driver said:


> You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?


The answer in my opinion. 



Spoiler



Turn off all he switches (if not already). Wait for a while to let all the bulbs cool down. Turn on one switch (lets say A). Wait 10 minutes. Switch A off. Turn on another on (say B). Open the door. The lit up bulb is controlled by B. The warm one is controlled by A and the remaining one is controlled by remaining switch (or C)


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## Orchid PE (Dec 17, 2019)

Dang it. I think that's right. Now I know I've heard this one before. But I dumb and forgot.


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## Audi Driver P.E. (Dec 17, 2019)

NikR_PE said:


> The answer in my opinion.
> 
> 
> 
> ...


Basically correct.


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## Orchid PE (Dec 17, 2019)

This is an oldie, so I'm sure most people know it:

You are in a room with two guards, each guarding a door. One of the doors leads to Heaven and the other to Hell, but you don't know which one leads where. You have to choose and open one of these doors, but you can only ask a *single *question to *one* of the guards. One of the guards always tells the truth and the other always lies, but you don't know which one is lying or telling the truth.

What do you ask to find out which door leads to Heaven?


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## Audi Driver P.E. (Dec 17, 2019)

Chattaneer PE said:


> This is an oldie, so I'm sure most people know it:
> 
> You are in a room with two guards, each guarding a door. One of the doors leads to Heaven and the other to Hell, but you don't know which one leads where. You have to choose and open one of these doors, but you can only ask a *single *question to *one* of the guards. One of the guards always tells the truth and the other always lies, but you don't know which one is lying or telling the truth.
> 
> What do you ask to find out which door leads to Heaven?


You ask one what the other one would say to do and then do the opposite.


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## Orchid PE (Dec 18, 2019)

Audi driver said:


> You ask one what the other one would say to do and then do the opposite.


Maybe? Do you have the exact question you would ask?


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## NikR_PE (Dec 18, 2019)

Chattaneer PE said:


> Maybe? Do you have the exact question you would ask?


Maybe something like. "If I asked the other guard which door will lead to heaven, what would they say?"


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## Orchid PE (Dec 18, 2019)

NikR_PE said:


> Maybe something like. "If I asked the other guard which door will lead to heaven, what would he say?"


This would work, because with this question asking either guard would point you to the hell door.


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## Orchid PE (Dec 27, 2019)

What is the next number in the sequence: 1, 11, 21, 1211, 111221, 312211, ???


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## Orchid PE (Feb 28, 2020)

Anyone have any more puzzles?


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