Probability of No Collision












2












$begingroup$


Four Athletes are standing at the vertices of a square park.When a whistle is blown, each of the athletes starts running along the side of the park at a speed of 20 Km/hr.The probability that they do no collide with each other is?



I am completely blank at this.



Please provide a clue to solve this.










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$endgroup$












  • $begingroup$
    If they all run clockwise or counterclockwise, they'll never collide.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:18










  • $begingroup$
    And Each one can do so independently with a probability of $frac{1}{2}$ right?
    $endgroup$
    – user3767495
    Jan 5 at 9:20










  • $begingroup$
    It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:20










  • $begingroup$
    I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
    $endgroup$
    – user3767495
    Jan 5 at 9:24






  • 1




    $begingroup$
    The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:25
















2












$begingroup$


Four Athletes are standing at the vertices of a square park.When a whistle is blown, each of the athletes starts running along the side of the park at a speed of 20 Km/hr.The probability that they do no collide with each other is?



I am completely blank at this.



Please provide a clue to solve this.










share|cite|improve this question









$endgroup$












  • $begingroup$
    If they all run clockwise or counterclockwise, they'll never collide.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:18










  • $begingroup$
    And Each one can do so independently with a probability of $frac{1}{2}$ right?
    $endgroup$
    – user3767495
    Jan 5 at 9:20










  • $begingroup$
    It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:20










  • $begingroup$
    I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
    $endgroup$
    – user3767495
    Jan 5 at 9:24






  • 1




    $begingroup$
    The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:25














2












2








2





$begingroup$


Four Athletes are standing at the vertices of a square park.When a whistle is blown, each of the athletes starts running along the side of the park at a speed of 20 Km/hr.The probability that they do no collide with each other is?



I am completely blank at this.



Please provide a clue to solve this.










share|cite|improve this question









$endgroup$




Four Athletes are standing at the vertices of a square park.When a whistle is blown, each of the athletes starts running along the side of the park at a speed of 20 Km/hr.The probability that they do no collide with each other is?



I am completely blank at this.



Please provide a clue to solve this.







probability






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 5 at 9:12









user3767495user3767495

3818




3818












  • $begingroup$
    If they all run clockwise or counterclockwise, they'll never collide.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:18










  • $begingroup$
    And Each one can do so independently with a probability of $frac{1}{2}$ right?
    $endgroup$
    – user3767495
    Jan 5 at 9:20










  • $begingroup$
    It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:20










  • $begingroup$
    I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
    $endgroup$
    – user3767495
    Jan 5 at 9:24






  • 1




    $begingroup$
    The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:25


















  • $begingroup$
    If they all run clockwise or counterclockwise, they'll never collide.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:18










  • $begingroup$
    And Each one can do so independently with a probability of $frac{1}{2}$ right?
    $endgroup$
    – user3767495
    Jan 5 at 9:20










  • $begingroup$
    It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:20










  • $begingroup$
    I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
    $endgroup$
    – user3767495
    Jan 5 at 9:24






  • 1




    $begingroup$
    The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
    $endgroup$
    – Raskolnikov
    Jan 5 at 9:25
















$begingroup$
If they all run clockwise or counterclockwise, they'll never collide.
$endgroup$
– Raskolnikov
Jan 5 at 9:18




$begingroup$
If they all run clockwise or counterclockwise, they'll never collide.
$endgroup$
– Raskolnikov
Jan 5 at 9:18












$begingroup$
And Each one can do so independently with a probability of $frac{1}{2}$ right?
$endgroup$
– user3767495
Jan 5 at 9:20




$begingroup$
And Each one can do so independently with a probability of $frac{1}{2}$ right?
$endgroup$
– user3767495
Jan 5 at 9:20












$begingroup$
It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
$endgroup$
– Raskolnikov
Jan 5 at 9:20




$begingroup$
It's not explicitly stated in the question, but I suppose that is indeed what you have to assume.
$endgroup$
– Raskolnikov
Jan 5 at 9:20












$begingroup$
I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
$endgroup$
– user3767495
Jan 5 at 9:24




$begingroup$
I think $frac{1}{2}$ is suitable because only two directions are possible and an athlete can choose only one at a time right?
$endgroup$
– user3767495
Jan 5 at 9:24




1




1




$begingroup$
The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
$endgroup$
– Raskolnikov
Jan 5 at 9:25




$begingroup$
The athlete could decide to prefer one direction over another, or he could decide to choose a direction with probability $pneqfrac{1}{2}$.
$endgroup$
– Raskolnikov
Jan 5 at 9:25










1 Answer
1






active

oldest

votes


















1












$begingroup$

To calculate the probability, we need to make an assumption about which direction each athlete runs. Let's assume, as you suggest, that




Each one can [run clockwise or counterclockwise] independently with a probability of $frac12$.




Now that this assumption is added to the problem, there are 16 possbilities: each of the four athletes can run Clockwise or Counterclockwise, and all $16$ possibilities are equally likely.



If one athlete runs Clockwise and another runs Counterclockwise then the two athletes will collide (convince yourself of this if it isn't clear).



So the only possibilities where the athletes do not collide are two:




  1. Clockwise, Clockwise, Clockwise, Clockwise


  2. Counterclockwise, Counterclockwise, Counterclockwise, Counterclockwise



That's $2$ out of $16$ equally-likely possibilities; therefore, the probability is $frac{2}{16} = frac{1}{8}$.






share|cite|improve this answer









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    $begingroup$

    To calculate the probability, we need to make an assumption about which direction each athlete runs. Let's assume, as you suggest, that




    Each one can [run clockwise or counterclockwise] independently with a probability of $frac12$.




    Now that this assumption is added to the problem, there are 16 possbilities: each of the four athletes can run Clockwise or Counterclockwise, and all $16$ possibilities are equally likely.



    If one athlete runs Clockwise and another runs Counterclockwise then the two athletes will collide (convince yourself of this if it isn't clear).



    So the only possibilities where the athletes do not collide are two:




    1. Clockwise, Clockwise, Clockwise, Clockwise


    2. Counterclockwise, Counterclockwise, Counterclockwise, Counterclockwise



    That's $2$ out of $16$ equally-likely possibilities; therefore, the probability is $frac{2}{16} = frac{1}{8}$.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      To calculate the probability, we need to make an assumption about which direction each athlete runs. Let's assume, as you suggest, that




      Each one can [run clockwise or counterclockwise] independently with a probability of $frac12$.




      Now that this assumption is added to the problem, there are 16 possbilities: each of the four athletes can run Clockwise or Counterclockwise, and all $16$ possibilities are equally likely.



      If one athlete runs Clockwise and another runs Counterclockwise then the two athletes will collide (convince yourself of this if it isn't clear).



      So the only possibilities where the athletes do not collide are two:




      1. Clockwise, Clockwise, Clockwise, Clockwise


      2. Counterclockwise, Counterclockwise, Counterclockwise, Counterclockwise



      That's $2$ out of $16$ equally-likely possibilities; therefore, the probability is $frac{2}{16} = frac{1}{8}$.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        To calculate the probability, we need to make an assumption about which direction each athlete runs. Let's assume, as you suggest, that




        Each one can [run clockwise or counterclockwise] independently with a probability of $frac12$.




        Now that this assumption is added to the problem, there are 16 possbilities: each of the four athletes can run Clockwise or Counterclockwise, and all $16$ possibilities are equally likely.



        If one athlete runs Clockwise and another runs Counterclockwise then the two athletes will collide (convince yourself of this if it isn't clear).



        So the only possibilities where the athletes do not collide are two:




        1. Clockwise, Clockwise, Clockwise, Clockwise


        2. Counterclockwise, Counterclockwise, Counterclockwise, Counterclockwise



        That's $2$ out of $16$ equally-likely possibilities; therefore, the probability is $frac{2}{16} = frac{1}{8}$.






        share|cite|improve this answer









        $endgroup$



        To calculate the probability, we need to make an assumption about which direction each athlete runs. Let's assume, as you suggest, that




        Each one can [run clockwise or counterclockwise] independently with a probability of $frac12$.




        Now that this assumption is added to the problem, there are 16 possbilities: each of the four athletes can run Clockwise or Counterclockwise, and all $16$ possibilities are equally likely.



        If one athlete runs Clockwise and another runs Counterclockwise then the two athletes will collide (convince yourself of this if it isn't clear).



        So the only possibilities where the athletes do not collide are two:




        1. Clockwise, Clockwise, Clockwise, Clockwise


        2. Counterclockwise, Counterclockwise, Counterclockwise, Counterclockwise



        That's $2$ out of $16$ equally-likely possibilities; therefore, the probability is $frac{2}{16} = frac{1}{8}$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 5 at 9:41









        60056005

        36.1k751125




        36.1k751125






























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