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Math Help - probabilty of choosing squares in diagonal

  1. #1
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    probabilty of choosing squares in diagonal

    Hello ,
    This my first post here.


    Two blocks are chosen randomly on a chess board. What is the probability that they lie on the same diagonal?

    2 blocks can be chosen in 64C2 ways .
    now we have to choose 2 blocks that lie in the same diagonal.
    this can be done in 2 x 8C2 ways (as there are 2 diagonals)
    so the probability is 56/2016. this is wrong according to the book.
    Thank you
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  2. #2
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    Quote Originally Posted by kannan View Post
    Hello ,
    This my first post here.


    Two blocks are chosen randomly on a chess board. What is the probability that they lie on the same diagonal?
    Are you sure they are talking only about the main diagonal?
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  3. #3
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    Quote Originally Posted by Isomorphism View Post
    Are you sure they are talking only about the main diagonal?
    oh i must have gone wrong there and is this answer right if they are talking about the main diagonal?
    Thank you very much
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  4. #4
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    Quote Originally Posted by kannan View Post
    oh i must have gone wrong there and is this answer right if they are talking about the main diagonal?
    Yes for the 'main diagonal' that is correct.
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