Question 1140037
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From the condition,


    - the probabilities to have G or R at the first intersection are each equal to  {{{1/2}}};


    - if there is R at the first intersection, then the probability to have R at the second intersection is  {{{2/3}}},  
         while the probability to have G at the second intersection is {{{1/3}}}.



From it, the probability under the question is 


    {{{(1/2)*(1/3)}}} = {{{1/6}}}.      <U>ANSWER</U>
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