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Thread: Probability DS

  1. #1
    Trying to make mom and pop proud
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    Probability DS

    What is the probability that a student randomly selected from a class of 60 students will
    be a male who has brown hair?
    (1) One-half of the students have brown hair.
    (2) One-third of the students are males.

    I thought it was C

    SPOILER:
    Official Answer is E

  2. #2
    Eager!
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    Let's call B the brown hair and M the males. Not-B are Blonde, Red,... F are females. Now draw the table:

    ______|__M___|___F__|___Total__
    B_____|__X___|_______|____30___
    Not-B |_______|_______|____30___
    Total _|__20___|___40__|____60___

    In red, the data provided or deduced from Proposition 1
    In blue the one provided by proposition 2

    We're looking for X (student simultanously Males AND with Brown hair), since the probability we're looking for is X/60.
    Obviously, we can't find X without an additional information. X can take any value from 0 to 20.

    Therefore Both propositions are NOT sufficient. Answer E
    Last edited by Fabrisco; 10-17-2006 at 10:59 PM.

  3. #3
    Eager!
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    In short, just think ... what if no male has brown hairs
    Bingo!! Solved

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