Orochi663 Posted June 9, 2013 Report Share Posted June 9, 2013 Hi, I once read over the internet a question like: You have a knife which is very sharp and a rope of unifoirm length, with a single cut what is the probability that the rope is cut exactly from half. The who gave the answer 1/3 had the logic that there are only three possibilities of this experiment after the cut. 1. Left peice is bigger 2. right peice is bigger 3. left peice = right peice so the probability he calculated is 1/3. When i discussed with some of my friends they were not convinced on this answer, arguing that this type of experiment can have infinite possibilities. Can someone please help and explain the correct answer if it exist at all. Regards Quote Link to comment Share on other sites More sharing options...

0 kingofpain Posted June 9, 2013 Report Share Posted June 9, 2013 The probability that the cut us exactly in the middle is precisely 0. However, if you impose a tolerance, then you will receive a finite answer. e.g. Rope is 10m long. The equality is defined as length of left side is equal to right side within 1 mm. This means that cutting anywhere from 4999.5mm to 5000.5mm will be ok. Therefore, the probability will be 1 in 10,000 if the probability of the cut at any point on the rope is equal. Cheers! 1 Quote Link to comment Share on other sites More sharing options...

0 Anza Power Posted June 9, 2013 Report Share Posted June 9, 2013 The who gave the answer 1/3 had the logic that there are only three possibilities of this experiment after the cut. 1. Left peice is bigger 2. right peice is bigger 3. left peice = right peice so the probability he calculated is 1/3. Ok, so by that logic if I go and fill out the lottery, there are 2 possibilities, either I win or I lose, so probability of me winning is 1/2... But yeah as kingofpain said, the probability is 0, you can think of it like this: the rope is 1 meter long and you pick a number between 0 and 1 and slice there, now, how many numbers are there between 0 and 1? (even if you think of the rope in a 3D space and give it a diameter the answer doesn't change) 2 Quote Link to comment Share on other sites More sharing options...

0 dark_magician_92 Posted June 10, 2013 Report Share Posted June 10, 2013 i agree to the anza and kop. Tha answer can't be 1/3 because the concept is that if you divide the case in 3 possibilities and all cases have equal possibilities, only then one of the case has the prob = r/y. Hence in this case prob. Of cutting in middle is not as same as cutting less than or more than half, so 1/3 doesnt work. 1 Quote Link to comment Share on other sites More sharing options...

0 witzar Posted June 10, 2013 Report Share Posted June 10, 2013 there are only three possibilities of this experiment after the cut. 1. Left peice is bigger 2. right peice is bigger 3. left peice = right peice so the probability he calculated is 1/3 It would be true, if all three possibilities were equally probable. Which is not the case. 1 Quote Link to comment Share on other sites More sharing options...

0 bonanova Posted June 11, 2013 Report Share Posted June 11, 2013 It's the probability of picking the number 0.500... from all the real numbers in [0, 1]. 2 Quote Link to comment Share on other sites More sharing options...

0 Orochi663 Posted June 14, 2013 Author Report Share Posted June 14, 2013 Thanks guys...Analogoy by Bonanva really helped understanding the answer of king of pain. Best Regards to All. Quote Link to comment Share on other sites More sharing options...

0 Orochi663 Posted June 14, 2013 Author Report Share Posted June 14, 2013 Any moderator reading this, please help me out, i am trying to Mark Solved multiple answers but now i cannot mark any of the answers as solved. Quote Link to comment Share on other sites More sharing options...

0 bonanova Posted June 17, 2013 Report Share Posted June 17, 2013 Try again. It seems to work now. Or tell me the post number and I'll do it. Quote Link to comment Share on other sites More sharing options...

0 Engeeni Posted September 14, 2020 Report Share Posted September 14, 2020 The answer is not zero, but you would need more information, like cross sectional area, length, weight or density of material, and molar mass of material. Relativisticly speaking it is infinitesimally close to zero, but definitely not zero, because we can predict the number of atoms or molecules, which is a lot... there is one factor that is 50/50 and that is whether there is an odd number or even number of atoms/molecules. imagine it like this, you are the size of an atom , you see a rope of 3 similar atoms bonded the probability becomes zero, just like if you had one atom...unless your knife is capable of splitting atoms the probability is 0... 2 atoms bonded your probabibility went up to one. 4 atoms and your probability is 3:7, as the number of atoms goes higher the probability drops. Quote Link to comment Share on other sites More sharing options...

## Question

## Orochi663

Hi,

I once read over the internet a question like:

You have a knife which is very sharp and a rope of unifoirm length, with a single cut what is the probability that the rope is cut exactly from half.

The who gave the answer 1/3 had the logic that there are only three possibilities of this experiment after the cut.

1. Left peice is bigger

2. right peice is bigger

3. left peice = right peice

so the probability he calculated is 1/3.

When i discussed with some of my friends they were not convinced on this answer, arguing that this type of experiment can have infinite possibilities.

Can someone please help and explain the correct answer if it exist at all.

Regards

## Link to comment

## Share on other sites

## 9 answers to this question

## Recommended Posts

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.