Red and Blue marbles interview puzzle

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You have two jars, 50 red marbles, 50 blue marbles. you need to place
al the marbles into the jars such that when you blindly pick one marble out of
one jar, you maximize the chances that it will be red. (when picking, you’ll first
randomly pick a jar, and then randomly pick a marble out of that jar) you can
arrange the marbles however you like, but each marble must be in a jar.
Put some load on you brain solution is not much hard to think.

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  • 1 Answer(s)

    You just have to think about various way by which you can maximize the probability of picking a red marble is maximised. Here’s one way :
    Put single red marble in Jar B and all other marbles in Jar A.
    so the probability of selecting a red marble is now :
    P(red) = P( Jar1 ) * P( red Jar1 ) + P( Jar2 ) * P( red Jar2 )
    P(red) = 0.5 * 1 + 0.5 * 49/99
    P(red) = 0.7474

    pnikam Expert Answered on 22nd August 2015.
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