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Brainteaser and math puzzle thread Brainteaser and math puzzle thread

07-09-2011 , 02:57 AM
The biggest and baddest brain teaser I know I have posted like two times already in the past.

There are two men and two numbers A and B.
  • Man 1 knows the product of these numbers (A*B)
  • Man 2 knows the sum of both numbers (A+B)
  • A and B are whole numbers (natural, what do you call it)
  • A and B are >1 and their sum <100.
The following conversation develops.
  • Man 1: I see the product of the numbers, but I don´t know the numbers A or B
  • Man 2: I knew you´d say that
  • Man 1: In that case, now I know the numbers
  • Man 2: In that case, now I know the numbers too.

What are A and B?
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07-09-2011 , 03:03 AM
Quote:
Originally Posted by bojtun
How many horsdes have won the tripleCrown?

Srsly
Quote:
Originally Posted by bojtun
Which Presidengt is on the $100 BILL?
YA gabe wins the thread vs. boj but imk shiot faced....


so answer mine?

eswpecially the triple crown one 8(with no research)

the other one is ez
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07-09-2011 , 03:13 AM
ok now im pissed . . .

midnight startds the day .. hANDS AT 12 AND 12, that's one

then 1:05 for two
2:10 for three
3:15 for four
4:230 YAYAYAYAY for fiver
5:25 for sicx
6:30 for 7
7:35 for eight
8:40 fpr nine
9:45 for 10
1050 for 11
1155 for 12
1200 for 13

gadamit is it 25?

K KEEP ON TRUCKING
105 for 14
210 for 15
315for 16
420 YAY for 17
525 for 18
630 for 19
735 for 20
\840 for 21
945 for 22
1050 for 23
1155 for 24



wtf im drunk and that was too ez so im obv wrong

if im not gabe owes me an apology imo
Brainteaser and math puzzle thread Quote
07-09-2011 , 03:15 AM
Quote:
Originally Posted by bojtun
1155 for 12
1200 for 13
lol @ your clock
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07-09-2011 , 03:16 AM
lol @ my face


GHET IT????
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07-09-2011 , 03:17 AM
anfd my hands

This forum requires that you wait 25 seconds between posts. Please try again in 16 seconds.
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07-09-2011 , 03:17 AM
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twss or somwething
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07-09-2011 , 03:18 AM
Brainteaser and math puzzle thread Quote
07-09-2011 , 03:18 AM
those were all ish times ftw
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07-09-2011 , 03:19 AM
if u gys want meto win this thread I will.

Just ask
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07-09-2011 , 03:27 AM
NO ****ING RESEARCH or spoils for ppl who know!!!

jackl and jill went up the hill eachj with a buck nd a quaryer ... what happened?
Brainteaser and math puzzle thread Quote
07-09-2011 , 03:28 AM
Spoiler:
if ur answer doesnt end w "OHHH" u lose
Brainteaser and math puzzle thread Quote
07-09-2011 , 08:11 AM
Quote:
Originally Posted by Gabethebabe
The biggest and baddest brain teaser I know I have posted like two times already in the past.

There are two men and two numbers A and B.
  • Man 1 knows the product of these numbers (A*B)
  • Man 2 knows the sum of both numbers (A+B)
  • A and B are whole numbers (natural, what do you call it)
  • A and B are >1 and their sum <100.
The following conversation develops.
  • Man 1: I see the product of the numbers, but I don´t know the numbers A or B
  • Man 2: I knew you´d say that
  • Man 1: In that case, now I know the numbers
  • Man 2: In that case, now I know the numbers too.

What are A and B?
this was posed way back in one of the first threads of this type. Can't remember if anyone solved it, I sure didn't.
Brainteaser and math puzzle thread Quote
07-09-2011 , 09:17 AM
Quote:
Originally Posted by ibavly
Please spoiler your answers. People should be able to read through this thread without having the answers revealed to them.
Quote:
Originally Posted by theHuntContinues
Spoiler:
ok

HAHahahahaa i dunno why but i was lol'n hard after reading this ^
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07-09-2011 , 11:29 AM
gabe, just to clarify a and b are in the interval 2-97, correct?
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07-09-2011 , 11:31 AM
Technically they're in the interval 2-97 I assume, since they sum to < 100.

Your ninja edit makes me look stupid.
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07-09-2011 , 11:38 AM
yeah I just realized it was the sum that was less than 100 not the numbers. Just wanted to make sure neither of the boundaries were supposed to be included.
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07-09-2011 , 11:51 AM
Intuitively I think including 1 would result in too many possible products for it to work so I think that must be out. I'm not sure about them summing to 100 though.

One thing I did want to clarify though was whether A could be the same as B (and possibly more importantly whether the men know this).
Brainteaser and math puzzle thread Quote
07-09-2011 , 12:03 PM
Quote:
Originally Posted by Willd
One thing I did want to clarify though was whether A could be the same as B (and possibly more importantly whether the men know this).
I would assume so.

I actually think I'm having a bit of a breakthrough with this, and hopefully should be able to solve it. It's just gonna take some time.
Brainteaser and math puzzle thread Quote
07-10-2011 , 03:29 AM
Quote:
Originally Posted by mute
It's just gonna take some time.
this
it takes time going 3 levels deep in recursion calculating with stuff like primes and their sums etc.
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07-10-2011 , 04:37 AM
Hmm so I'm going brute force method. Seems like it should be fairly straightforward to solve. Down from around 9k numbers to about 2k. Not sure why I'm doing this lol.

Is there a clever way to solve this, or do you pretty much have to just do eliminations?
Brainteaser and math puzzle thread Quote
07-10-2011 , 05:39 AM
Quote:
Originally Posted by ibavly
Hmm so I'm going brute force method. Seems like it should be fairly straightforward to solve. Down from around 9k numbers to about 2k. Not sure why I'm doing this lol.

Is there a clever way to solve this, or do you pretty much have to just do eliminations?
this seems like an easier brute force method, but likely also not the right way to solve it:

Spoiler:

What I'm doing is this: Start with from the bottom with sums, and see which sums make the second statement possible.

Example: For the sum 11 there are four possibilities: 2+9, 3+8, 4+7, 5+6. In order for statement 2 to be possible, there has to be more than one way to get the product of all of these via multiplication. So 2*9=18, but you can also get that from 3*6. 3*8=24 but you can also get that from 2*12 or 6*4. 4*7=28 but you can get that from 2*14. 5*6=30, but you can also get that from 3*10 or 2*15. So 11 would be a candidate sum.

For 13 you get 2*11=22, but there is no other way to get 22 so 13 is not a candidate.

This still gets very cumbersome as the sums get bigger though, and from gabes post I would guess, there's a simpler way.

Once you have the candidate sums, write down the possible products for all of them. Hopefully you should be able to tell which products makes it possible for A to know the numbers, and hopefully knowing that that helps B to know the numbers, you can figure out what the numbers are.
Brainteaser and math puzzle thread Quote
07-10-2011 , 07:47 AM
Spoiler:
I started working on a very similar method to mute but didn't get far with it because the number of possible sums for the higher numbers is so large. One thing I have just realised though is that you can immediately eliminate any sum that can be made by summing 2 primes, because the product of them will be unique. This means that any prime +2, +3, +5, etc can't be the correct sum, which cuts down on the possibilities quite significantly.
Brainteaser and math puzzle thread Quote
07-10-2011 , 10:16 AM
Quote:
Originally Posted by Willd
Spoiler:
I started working on a very similar method to mute but didn't get far with it because the number of possible sums for the higher numbers is so large. One thing I have just realised though is that you can immediately eliminate any sum that can be made by summing 2 primes, because the product of them will be unique. This means that any prime +2, +3, +5, etc can't be the correct sum, which cuts down on the possibilities quite significantly.
Oh yeah, that's very helpful.

Spoiler:
I already suspected, that all even numbers were out, but having really given much thought to proving why, but you can make any even sum by adding 3, 5 or 7 to another prime.


edit:
Spoiler:
except for 98, which is 79+19
Brainteaser and math puzzle thread Quote
07-10-2011 , 02:11 PM
Think I may have solved it but just wanna confirm before I write a long post full of nonsense:

gabe is the answer:

Spoiler:
3 and 14
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