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Thread: Icosahedron

  1. #1
    Super Member harpazo's Avatar
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    Icosahedron

    A special die is made in the shape of an icosahedron, and its faces are numbered with the numbers 1 to 20.
    When the die is thrown there is an equal chance of any face landing uppermost. If the die is thrown once, what is the probability that the face that lands uppermost has a number that is a factor of 20?

    Solution:

    Factors of 20: 1, 2, 4, 5, 10, 20

    Let A = probability that the face that lands uppermost has a number that is a factor of 20.

    P(A) = 6/20 = 3/10

    My answer is 3/10.

    Is this right?
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  2. #2
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    Re: Icosahedron

    Yes, it is.
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  3. #3
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    Re: Icosahedron

    Quote Originally Posted by harpazo View Post
    A special die is made in the shape of an icosahedron, and its faces are numbered with the numbers 1 to 20.
    When the die is thrown there is an equal chance of any face landing uppermost. If the die is thrown once,
    what is the probability that the face that lands uppermost has a number that is a factor of 20?
    Why do problem setters not keep it simple; like:

    A deck of 20 cards, cards labelled 1 to 20.
    Deck shuffled, a card then picked at random.
    What is the probability that a number that is a factor of 20 is picked?
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  4. #4
    Super Member harpazo's Avatar
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    Re: Icosahedron

    Quote Originally Posted by HallsofIvy View Post
    Yes, it is.
    Ok. Another one for my notes.
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