Sven's Official BrainTeaser Thread !! and Sander.

[sputnik]

not sure i understand mikes riddle, but is it 126?

[VG]

whoops i got the answer wrong i think its A) for the reasons i stated the first time

[Sander]

for the amount of tatw's with the different combinations you get 2^n  with 2 being the options (left or right) and n being the amount of tatw's
so the answer is 2^99 + 2^100

[Mike]

for the amount of tatw's with the different combinations you get 2^n  with 2 being the options (left or right) and n being the amount of tatw's
so the answer is 2^99 + 2^100

That is not correct, eventhough it's close. Why do you add 2^100? (not adding 2^100 is not the correct answer) In this story, he doesn't try 100 tatws in any way. He just want's to be able to do 100 tatws

[Sander]

for the amount of tatw's with the different combinations you get 2^n  with 2 being the options (left or right) and n being the amount of tatw's
so the answer is 2^99 + 2^100

That is not correct, eventhough it's close. Why do you add 2^100? (not adding 2^100 is not the correct answer) In this story, he doesn't try 100 tatws in any way. He just want's to be able to do 100 tatws

okay mike, now i see it. i think it's (2^99)+1

[Mike]

for the amount of tatw's with the different combinations you get 2^n  with 2 being the options (left or right) and n being the amount of tatw's
so the answer is 2^99 + 2^100

That is not correct, eventhough it's close. Why do you add 2^100? (not adding 2^100 is not the correct answer) In this story, he doesn't try 100 tatws in any way. He just want's to be able to do 100 tatws

okay mike, now i see it. i think it's (2^99)+1

Nah, wrong again. Why do you add 1?

Ok I'ma just tell you the answer. 2^99 = the amount of combinations there are. There are 99 tatws in each combination. So 99*2^99 would be the answer.

[Rodrigo]

here you got another one..

Imagine that you are walking alone through a park.. then you find 2 ways to go.. one way takes you to the right place.. and the other one takes you to the wrong place.. there you meet 2 policemen.. one of those always says the truth but.. at the same time the other one always lies.. you can ask one "just one of them" "just one question".. WHO WOULD YOU CHOOSE? AND WHAT WOULD YOU ASK? to follow the correct way.

Good luck

[sputnik]

ask either one, which way would the other policeman tell me to go?

the liar tells a lie, and says the truthteller would tell me the wrong way
the truth teller tells the truth, and says the liar would tell me the wrong way

so you go the opposite way to whoever you ask

[Sander]

i think a similar one has been asked before, but it's correct.
and mike i don't know if your calculation is correct, but we won't start mathematical discussions here ;)
someone feel free to post a nice riddle

[Mike]

and mike i don't know if your calculation is correct, but we won't start mathematical discussions here ;)

But please, tell me why it's wrong. I made that one up myself so I don't have a key for it really.

Another one:

A train is travelling with a constant speed. A car going 15 m/s the opposit direction of the train passes the train in 12 seconds. Another car going 20 m/s in the same direction as the train passes the train in 72 seconds. What's the speed and length of the train?

[sputnik]

train is 14m/s distance is 12m? i really confused myself doing this lol

edit: lol no this is very wrong.. i shouldnt try doing two things at once

edit 2: solved now i have my full attention :P

20-v=DT(1)   DT(1) is difference in time of the car going same way as the train
15+v=DT(2)  DT(2) is difference in time of the car going different way as the train

DT2*12=S     going at difference in time 2, for 12 seconds= passing the distance of train
DT1*72=S     going at difference in time 1, for 72 seconds= passing the distance of train

(15+v)*12=S    subsituting from the first set of eqs into the second gives these new equations
(20-v)*72=S

180+12v=S      multiplying out the brackets gets you these simplifications
1440-72v=S

180+12v=1440-72v   putting the two equations equal to each other and rearranging get you this
180-1440=-72v-12v
-1260=-84v
v=15m/s

so the trains going at 15m/s and the car going the same way as it at 20m/s... the car takes 5m/s out of the train for 72 seconds passing it, so the train is 72*5 which is 360m long.

checking, the train is going 15m/s and the car going the opposite way is going at 15m/s... so taking 30meters out of the train every second for 12 seconds. 30*12= 360m. prooved

[Mike]

train is 14m/s distance is 12m? i really confused myself doing this lol

edit: lol no this is very wrong.. i shouldnt try doing two things at once

edit 2: solved now i have my full attention :P

20-v=DT(1)   DT(1) is difference in time of the car going same way as the train
15+v=DT(2)  DT(2) is difference in time of the car going different way as the train

DT2*12=S     going at difference in time 2, for 12 seconds= passing the distance of train
DT1*72=S     going at difference in time 1, for 72 seconds= passing the distance of train

(15+v)*12=S    subsituting from the first set of eqs into the second gives these new equations
(20-v)*72=S

180+12v=S      multiplying out the brackets gets you these simplifications
1440-72v=S

180+12v=1440-72v   putting the two equations equal to each other and rearranging get you this
180-1440=-72v-12v
-1260=-84v
v=15m/s

so the trains going at 15m/s and the car going the same way as it at 20m/s... the car takes 5m/s out of the train for 72 seconds passing it, so the train is 72*5 which is 360m long.

checking, the train is going 15m/s and the car going the opposite way is going at 15m/s... so taking 30meters out of the train every second for 12 seconds. 30*12= 360m. prooved

Nicely done :thumbsup: , it's correct indeed :thumbsup: .