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Math Help - valid,non valid arguments

  1. #1
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    valid,non valid arguments

    Prove which of the following arguments are valid or non valid:

    1)if London is in France then Paris is in England.But London is not in France,hence Paris is not in England.

    2)if London is in England then Paris is in France.But Paris is not in France ,hence London is not in England.

    3)if London is in France then Paris is in England.But London is in France, hence Paris is in England.

    Surely the 1st one is true,the 2nd one false and the 3rd one also false .

    But why do they ask us to prove that ,what is there to prove??
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  2. #2
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    Are my answers correct ,how do we prove them so??

    Please help.
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  3. #3
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    1)if London is in France then Paris is in England.

    But London is not in France,
    By some method you can prove this is true.
    Perhaps London is in Italy or Spain, but wherever it is,
    you can prove it is not in France.

    hence Paris is not in England.
    However, your london proof DOES NOT contradict
    the 2nd statement.

    Not a valid argument.
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  4. #4
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    Quote Originally Posted by aidan View Post
    1)if London is in France then Paris is in England.

    But London is not in France,
    By some method you can prove this is true.
    Perhaps London is in Italy or Spain, but wherever it is,
    you can prove it is not in France.

    hence Paris is not in England.
    However, your london proof DOES NOT contradict
    the 2nd statement.

    Not a valid argument.
    Thank you,although i do not fully understand your explanation.

    How about arguments 2 and 3?
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  5. #5
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    Quote Originally Posted by alexandros View Post
    Thank you,although i do not fully understand your explanation.

    How about arguments 2 and 3?
    Arguments (2) and (3) are valid arguments and argument (1) non valid one
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