Sven's Official BrainTeaser Thread !! and Sander.

[Mike]

Those were kind words. Thank you.

I have one for you all:

A man's sailing in a canoe. Firstly, he paddles against the stream to a point B. When reaching the point he decides to return to his initial point A, and does so by resting whilst floating along the stream. The time it takes to travel from A to B takes just as long as from B to A.

The next day he decides to go paddling again, but this time he's willing to paddle in both directions (he's not resting on his way back).

Which time should he turn back if he starts paddling at 4 and want's to get back at 8?

The conditions are the same as the day before.

[Max]

at 7

[sputnik]

Another shot in the dark:

If he's 5 meter away from the south pole, he'll be standing on the south pole when done. If you go north from the south pole you can go to whatever direction you wan't.
Macca decides he want's to create a triangle with one right angl. The distance from the flag (x) and the 3 m north are the short sides, whereas the 5 meter is the long side.

x^2=5^2-3^2
x^2=16
x=4

He's 5 meters away from the south pole.

Mike you're a true hero. Very well done, I knew if someone would find this one it would be you or Sputnik. Karma+

i did actually work this out ;(

[Mike]

Now I have to figure out wether it's a wild guess or you actually came across 7 after calculation.

I'm guessing the latter. Good job, but next time elaborate. :cheers:

A new one: (if you want to post a Brain teaser M4x, just do so and I'll withdraw mine)

A "boy" named Tom writes down two positive integers, a and b, with a sum not bigger than 11 (a+b<=11). "He" tells her boyfriend Besmira the sum of the numbers (a+b) and the product (a*b) to Matte.

Matte and Besmira engages a conversation:

Matte: I don't know the numbers

Besmira: I knew you wouldn't know!

Matte: In that case I know what the numbers are!

Besmira: Then I know too!

What numbers did Tommy write down?

'Tis a bit harder, but you can come up with it. I'm sure of it :thumbsup:

[TW89]

A girl named Tom writes down two positive integers, a and b, with a sum not bigger than 11 (a+b<=11). She tells her boyfriend Besmira the sum of the numbers (a+b) and the product (a*b) to Matte.

Woah, hold on right there! A girl named Tom o_O   I take offense lol A girl! Are you sure?

Fwiw I got 7 too.

[Mike]

Oh soz, I thought Tom was a girl´s name. I'll edit.
 
Sorry about that.

[TW89]

Oh soz, I thought Tom was a girl´s name. I'll edit.
 
Sorry about that.

Lol its okay. And lol @ the  "s


I havent got a clue either for yours...  :dontknow:

[sputnik]

i'll write down my thinking on this one though it seems very hard and ive probably made a massive oversight :\ plus its hard

the only numbers that besmira can figure out on their own are 2 and 3 (1+1 and 2+1). the rest can be more than one combination and therefore cannot be known or figured out.

the only numbers matte can figure out are 1, 2, 3, 5, 7, 14, 15, 20, 21, 25, 28 & 30

the only way that besmira can KNOW that matte wouldnt know, is that besmira knows what the two numbers are and can figure out its a number matte cannot know.

however the numbers besmira can figure out lead to a product of 1 or 2, both of which matte could figure out anyway.

so im confused.

Besmira
http://img248.imageshack.us/my.php?image=math2jk7.jpg

Matte
http://img187.imageshack.us/my.php?image=mathtg5.jpg

the key for both;

Orange= darkblue*yellow is <= 11
Red&Blue writing= having 2&10 is the same as 10&2. this creates one usuable number and one excess number. excess numbers are red, non excess are blue
Blue underlined writing= people can only work a number when it is the only thing possible. if there are two '10s' there are two combinations, and what made them cannot be determined. underlined means they CAN be determined.

[VG]

OK i have changed my answer to 8+2 i think i'll post my working if its right

[Mike]

i'll write down my thinking on this one though it seems very hard and ive probably made a massive oversight :\ plus its hard

the only numbers that besmira can figure out on their own are 2 and 3 (1+1 and 2+1). the rest can be more than one combination and therefore cannot be known or figured out.

the only numbers matte can figure out are 1, 2, 3, 5, 7, 14, 15, 20, 21, 25, 28 & 30

the only way that besmira can KNOW that matte wouldnt know, is that besmira knows what the two numbers are and can figure out its a number matte cannot know.

however the numbers besmira can figure out lead to a product of 1 or 2, both of which matte could figure out anyway.

so im confused.

Besmira
http://img248.imageshack.us/my.php?image=math2jk7.jpg

Matte
http://img187.imageshack.us/my.php?image=mathtg5.jpg

the key for both;

Orange= darkblue*yellow is <= 11
Red&Blue writing= having 2&10 is the same as 10&2. this creates one usuable number and one excess number. excess numbers are red, non excess are blue
Blue underlined writing= people can only work a number when it is the only thing possible. if there are two '10s' there are two combinations, and what made them cannot be determined. underlined means they CAN be determined.

Must Besmira know the numbers in order to know that Matte doesn't know?

Keep on going, you're getting there. :thumbsup:

And VG, the answer is not 8 + 2, but do please share your thoughts with us.

[SvenF]

This is more difficult than I thought at the beginning.. I'm not that good at riddles with numbers..

[Sander]

i think it's 4 and 6. tell me if i'm right or wrong. if i'm right i'll explain

and sorry for not updating the tread for a while. i kinda forgot about it too, just like sven and also the whole mathematical discussions were taking the overhand, what should not have happened (please don't continue about that, open new tread) (bad treadowners  :down:, we'll make it up)