Posted: May 25, 2009 in M@th puzzles
Tags: ,


You have two jars and 100 marbles. Fifty of the marbles are red, and 50 are blue. One of the jars will be chosen at random; then 1 marble will be withdrawn from that jar at random. How do you maximize the chance that a red marble will be chosen? (You must place all 100 marbles in the jars.) What is the chance of selecting a red marble when using your scheme?


  1. sushmita says:

    hi hottie ur puzzles r gr8 man…
    add some more man..

  2. sushmita says:

    hey are there any puzzles like marbles

  3. Namdor says:

    You put one red marble in one jar and the rest in the other one (49 red plus 50 blue). This way you maximize the probability to get a red marble (since you have 1/2 chance of choosing the jar with the red marble and 1/2 of choosing the other one. Then, 100% prob to get the red one if the jar with the red one is chosen and 49/99 chances of getting a red one if you choose the jar with the rest of the marbles).

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