

Subject:
Clarity of Thought (Part 1)
Category: Science > Math Asked by: mongoliaga List Price: $2.00 
Posted:
08 Jun 2006 17:10 PDT
Expires: 08 Jul 2006 17:10 PDT Question ID: 736540 
Two Integers greater than one. Standard knows the sum. Poor knows the product Standard Says 'One Thing is certain, you cannot have determined my sum.' Poor says after a suitable delay 'Thanks for telling me that but I still don't know your sum' Standard says after another delay 'And I don't know your product' Poor says 'But now I know your sum' What are the two integers? Mongolia  
 


There is no answer at this time. 

Subject:
Re: Clarity of Thought (Part 1)
From: berkeleychocolatega on 08 Jun 2006 19:37 PDT 
Here's my guess: x=y=2. Reason: The cryptic information essentially says that knowing the product or the sum one can obtain the other. Probably this means that xy = x+y. Say y=x+n. Assume n>0. Then x^2+nx=2x+n. But x^2>=2x and nx>n, contradiction. Therefore n=0 and x^2=2x. So x=y=2. 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 08 Jun 2006 19:55 PDT 
I would disagree with Berkeley, if standard knows the sum is 4 and poor knows the product is 4, then standard would not be able to say 'One Thing is certain, you cannot have determined my sum.' because with integers greater than 1 the only thing that sums to 4 is 2 and 2 allowing standard to know that the product is 4 meaning that poor would be looking at xy=4 x,y>1 which can of course only mean that x=y=2 so poor would already be able to know standards sum making the first quote false. 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 08 Jun 2006 21:16 PDT 
Product:30 Sum:17 Since poor is the solver of the game we look at it through his perspective of having 30 with factor pairs of 2*15 meaning S has 17 as sum 3*10 meaning S has 13 as sum 5*6 meaning S has 11 as sum When S says 'One Thing is certain, you cannot have determined my sum.' This has to be taken as the fact that he has a sum which CANNOT be made up of 2 primes, for it was then it would be possible poor would know right of the bat the product of 2 primes cannot be divisible by any other 2 numbers this means he cannot have 13 as a sum because that could be expressed as 2+11. Since P still has the possibility of the sum being either 17 or 11 he needs to say 'Thanks for telling me that but I still don't know your sum' Now when S responds 'And I don't know your product' We see that if he had 11 he would be able to verify our product because if we had: 2*9 = 18 with our possible choices for his sum being 11 or 9 we could have ruled out 9 in his original statement so we would have known it was 11 after his first hint 3*8 = 24 with our possible choices for his sum being 14 10 or 11 we could have ruled out 14 and 10 in his original statement so we would have known it was 11 after his first hint 4*7 = 28 with our possible choices for his sum being 16 or 11 we could have ruled out 16 in his original statement so we would have known it was 11 after his first hint Leaving our only option to be 5*6=30 However since he did say he didn?t know our product we need to verify that there are 2 possible different products if S had 17 as the sum. One possibility would of course be 17=2+15 =>2*15=30 another would be if P had 42 (3*14) then with all the given information P still wouldn?t be able to narrow it down since S would then be able to have either 17=3+14 or 23=2+21 (both of which I obviously chose since they cannot be the sum of 2 primes) Now since S said And I don?t know your product, which we?ve shown he would had he had 11 as the sum but unable to with 17 as the sum and those are our only 2 options we can positively state he has 11 as the sum and we have 30 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 08 Jun 2006 21:18 PDT 
hmmm I see I was typing that for a while, well cyn, can you at least tell me if I was close, not paying attention to my probably incomprehendable use of runons? 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 08 Jun 2006 22:06 PDT 
I also found the answer online just now and it didn't match up, I'd go through and try to find where I messed up but I have to do my own homework (3 papers due tomorrow) silly college and it making math majors take english courses, like I know how to read... 
Subject:
Re: Clarity of Thought (Part 1)
From: cynthiaga on 08 Jun 2006 22:13 PDT 
Nope, I can't tell ya, it's part of the game! Plus, I found a page that details all the places this question is found, all the variations and answers are discussed. Upon a quick skim, I think there are 3 correct answers, and being right would mean you figured out there are 3 and what they are. And I suspect you found the same or a similar page, because you are right, your answer needs a bit of reworking. However, I think college is more important than hanging out at GA waiting for interesting math questions! And you DO know how to read. 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 09 Jun 2006 10:26 PDT 
Hey Cynthia, did you find a page with the question as stated? I noticed just know that the one I was looking at was <<1>> Mr. P.: I do not know the two numbers. <<2>> Mr. S.: I knew that you didn't know the two numbers. <<3>> Mr. P.: Now I know the two numbers. <<4>> Mr. S.: Now I know the two numbers. which is a bit different the ours stated here. when I worked the Mr. P and Mr.S problem I got the correct answer. I haven't gone through all my math again as even I have trouble reading where I was going. Anyway, papers are done, no more classes for a month, and I get to sleep for 2 horus before working for 8 (woo hoo) so I'll check back tonight or tomorrow. 
Subject:
Re: Clarity of Thought (Part 1)
From: mongoliaga on 12 Jun 2006 18:32 PDT 
to MATHISFUNGA Just to let you know both your answer and reasoning by which you came upon the answer agrees completely with my source. i.e. Integers 2 and 15 (so sum is 17 and product is 30) If you had been a researcher you would have been entitled to the sum of 17 dollars (2 dollars for this question plus 15 dollars for the other question making a total sum of 17 dollars :) of course minus the Google Empire's commission) So congratulations and even though I cannot give the princely sum of 17 dollars, I am sure this exercise was intellectually much more simulating than your English Test. Cynthiaga If you really did find this same problem on the WEB could you send me the link? Regards to all Mongolia 
Subject:
Re: Clarity of Thought (Part 1)
From: mathisfunga on 12 Jun 2006 19:07 PDT 
Thanks Mongolia, I had reread my work and couldn't find any mistakes, but goo do know for sure I was right, it was indeed a fun problem! 
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