Open Side Menu Go to the Top
Register
Brainteaser and math puzzle thread Brainteaser and math puzzle thread

07-05-2011 , 08:11 AM
not to mention we can't play since if i run good and hit 1000 flips you won't be able to pay.
Brainteaser and math puzzle thread Quote
07-05-2011 , 08:30 AM
That will happen below 20 flips already
Brainteaser and math puzzle thread Quote
07-05-2011 , 09:22 AM
I think what you're supposed to do is convince someone to play this with you and you give them 3 dollars a flip or something.
Brainteaser and math puzzle thread Quote
07-05-2011 , 07:01 PM
Quote:
Originally Posted by ibavly
You have 3 people. One person always tells the truth, one always lies, one sometimes tells the truth sometimes lies. You can ask three questions. You ask each one one question, one person 2, w/e you want to do.

How do you figure out who is who?

btw I think it is a given that if you already know the riddle don't post the answer, if you solved it then you should probably still use spoilers.
did this in notebook so sorry if the formatting sucks

Spoiler:
T = Truth guy, L = Liar, B = Both truths and lies guy

6 Permutations

1 2 3
T L B
T B L
L T B
L B T
B T L
B L T

basically you wanna ask questions to either T or L because asking B is pointless. So try to ask questions that will make person is spot 1 2 or 3 either a T or an L

Q1: "First guy, is T is to the right of B or is L is in the middle?" (i.e. if one is true the answer is yes)

if YES, then it's

1 2 3
T L B
L T B
B L T
B T L

NOTE: in this case column 2 is either Ts or Ls so you're gonna ask him the next question

if NO, then it's

1 2 3
T B L
L B T
B L T
B T L

NOTE: in this case column 3 is either Ts or Ls so you're gonna ask him the next question
-----------------------------------------------------------------------------------------

So, if Q1 = yes, Q2 could be: "Second guy, are you the 'Both' guy"

if Yes, he's lying, so it's

1 2 3
T L B
B L T

if No, then he's telling the truth, so it's

1 2 3
L T B
B T L

Now if Q1 = no, Q2 could be: "Third guy, are you the 'Both' guy"

If Yes, he's lying, so it's

1 2 3
T B L
B T L

If No, he's telling the truth, so it's

1 2 3
L B T
B L T

----------------------------------------------------------------------------------------------
Q3 is the easiest, now that you know for sure that one of the spots is a liar or a truth guy so you just ask him who one of the other guys is and you'll know all 3.

for example, if you know guy lets say you ask Q1 and he says yes, and then ask Q2 and he says yes again. Therefore you know that guy 2 is a liar. Now ask him if guy 3 is a truth teller. If he says no, then you know guy 3 is the truth teller and guy 1 is the both guy.

you can do that for all the rest of them
Brainteaser and math puzzle thread Quote
07-05-2011 , 07:13 PM
edit: problem already answered
Brainteaser and math puzzle thread Quote
07-06-2011 , 01:14 PM
I declare myself King of Puzzle, Prince of Brainteaser and Lord of PoG.
Brainteaser and math puzzle thread Quote
07-06-2011 , 10:09 PM
Quote:
Originally Posted by bojtun
Spoiler:
Or 18?


Something is missing from the question.
Spoiler:
because there aren't multiple answers that add up to the same house #

9 + 2 + 2 = 13 and 6 + 6 + 1 = 13
Brainteaser and math puzzle thread Quote
07-07-2011 , 01:42 AM
Quote:
Originally Posted by ibavly
You have 3 people. One person always tells the truth, one always lies, one sometimes tells the truth sometimes lies. You can ask three questions. You ask each one one question, one person 2, w/e you want to do.

How do you figure out who is who?

btw I think it is a given that if you already know the riddle don't post the answer, if you solved it then you should probably still use spoilers.
is lining the three people up the only way to answer this one?

if you ask the liar "do you sometimes lie and sometimes tell the truth", would he say yes? edit: nevermind, i wouldn't be able to make progress using this method either way.
Brainteaser and math puzzle thread Quote
07-07-2011 , 03:00 AM
Spoiler:
you could ask, which of the other 2 is more likely to tell a lie. If he's the liar, he will point at the truth teller. If he's the truth teller, he will point at the liar. If he's random, you're not going to be asking him the next Q anyways so you're safe.
Brainteaser and math puzzle thread Quote
07-07-2011 , 10:44 PM
Quote:
Originally Posted by TheDean1
Feels like there should be one of these where people can just drop random brainteasers and try to answer them and whatnot. I'll go first:

In celebration of Mets's 75k post, he and HiFi decide to host a party and invite 10 other couples (22 total ppl at the shin dig) . Throughout the course of the party, Mets decided to keep track of the handshaking going on and surveyed the entire party (i.e. everyone including HiFi but not himself). Note that although Mets isn't part of the data sample directly, somebody else shaking his hand does count toward their respective tally. He found 2 noteworthy facts

1) Everybody that he surveyed shook a different number of hands
2) Nobody shook hands with their spouse/significant other/etc

How many hands did HiFi shake?
I love you Dean

I may or may not try to figure out the answer

But I love you regardless
Brainteaser and math puzzle thread Quote
07-07-2011 , 10:47 PM
They need to fix the spoiler thing on this 2+2 app asap
Brainteaser and math puzzle thread Quote
07-07-2011 , 10:47 PM
Quote:
Originally Posted by crazyk951
awesome thread, keep it up!
Do I need to even say it?
Brainteaser and math puzzle thread Quote
07-08-2011 , 06:27 AM
Quote:
Originally Posted by metsandfinsfan
Do I need to even say it?
say what mets...?
Brainteaser and math puzzle thread Quote
07-08-2011 , 08:22 AM
The Truel

Three guys are fighting over TimeLady and they agree to decide with a "truel" (thats a duel of three ). All three get a gun and last man standing wins.
Man 1 shoots pretty bad. 1 in 3 kill
Man 2 shoots better. 2 in 3 kill
Man 3 shoots perfect - 3 in 3 kill = 100%

They agree to shoot one at a time. First the worst shooter (Man1) followed by Man2 (if alive), followed by Man3 (if alive), after which the cycle repeats.

We assume that a hit = death and a miss = complete miss.

You are Man 1. What do you do.

For the mathematicians: What are the probabilities of Man1, 2 and 3 to win this truel?
Brainteaser and math puzzle thread Quote
07-08-2011 , 09:10 AM
gtb i assume you can shoot at whomever you choose, correct?
Brainteaser and math puzzle thread Quote
07-08-2011 , 09:12 AM
Quote:
Originally Posted by Wyman
gtb i assume you can shoot at whomever you choose, correct?
Yes, that is the question.
Brainteaser and math puzzle thread Quote
07-08-2011 , 09:16 AM
I like TL and all, but I'm probably just gonna let the other two shoot it out.
Brainteaser and math puzzle thread Quote
07-08-2011 , 09:33 AM
Spoiler:
To answer the first question:

Seems to me, that you can just ignore the misses, since it doesn't matter who you would be shooting at then.

So all it comes down to is kill man 2 -> get killed 100%, kill man 3 -> get killed <100%.

Will look at the exact %'s unless this is wrong.
Brainteaser and math puzzle thread Quote
07-08-2011 , 09:45 AM
oh wait a sec

Spoiler:
man 1 should miss on purpose, I think
Brainteaser and math puzzle thread Quote
07-08-2011 , 10:12 AM
Spoiler:
After miss by man 1:

Scenario 1, man 2 shoots man 3 (67%):

1/3+(2/3*1/3*1/3)+(2/3*1/3*2/3*1/3*1/3)+(2/3*1/3*2/3*1/3*2/3*1/3*1/3)....~43%

Scenario 2, man 2 misses is then killed by man 3 (33%):

Man 1 gets one shot to kill man 3=33%

Total chance of survival: (67%*43%)+(33%*33%)~39.8%

If he shoots at man 3 he has (67%*39.8%)+(33%*33%*43%)~31.3%

Man 1 wins 39.8%
Man 3 wins: (1/3*2/3) ~ 22.2%
Man 2 wins: (2/3*57%) ~ 38%
Brainteaser and math puzzle thread Quote
07-08-2011 , 10:22 AM
Spoiler:
Yes man 1 should intentionally miss, and mute's analysis is right up to a sig fig or so. It is trickier to compute this if there is an arbiter who will shoot you if you miss intentionally. So there's my bonus add-on. If you try to compute this, you should get:
Spoiler:
M1 will then win 59/189 times, M2 34/63, and M3 4/27.
Brainteaser and math puzzle thread Quote
07-08-2011 , 11:14 AM
Can't believe I have been missing this thread. Here is a nice problem that I just recently heard. It is more of an algorithm problem than it is a math problem or a brain teaser, but hopefully some of you will find it interesting to think about. The solution isn't easy.

Suppose you have a stack of n cards labeled 1 to n, and initially they are arranged in order with card 1 on top and card n on bottom. Consider the following shuffling procedure:

--------------------------------
Repeat the following two steps until all cards are on the table:

1) Place the card on the top of the deck on a table.
2) Place the next card on the bottom of the deck.
---------------------------------


The problem: compute the number of iterations of this procedure until the cards are back in order on the table for any integer n > 0.

One way to do this is to simulate the procedure as many times as it takes to get back to the initial configuration (this will terminate for any n). However this will take a very long time for large n. There is a way of computing this that is much faster. What is it?

Just to be clear, the solution should not be a number, but rather a function that takes as input the number of cards and returns as output the the correct answer.
Brainteaser and math puzzle thread Quote
07-08-2011 , 11:41 AM
Just to be clear about the problem, assuming n = 2 the number of iterations would be 4 right?

Code:
Iteration | Deck | Table
0         | 1,2  | 
1         | 2    | 1
2         |      | 2,1
3         | 1    | 2
4         |      | 1,2
Brainteaser and math puzzle thread Quote
07-08-2011 , 11:42 AM
I think that is 2 iterations, but I'll let him clarify.
Brainteaser and math puzzle thread Quote
07-08-2011 , 11:47 AM
Each iteration in that is doing both parts; putting a card on the table and putting the next card on the bottom, it's just that obviously putting the top card on the bottom doesn't do anything when there's one or zero cards left in the deck.
Brainteaser and math puzzle thread Quote

      
m