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Red ball... Red ball (Posted on 2002-10-17) Difficulty: 4 of 5
If you take two balls randomly out of a jar of colored balls, there is a 50% chance that the balls will both be red.

What is the total percentage of red balls in the jar?

See The Solution Submitted by levik    
Rating: 3.1538 (13 votes)

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Some Thoughts Not everything appears as it seems | Comment 14 of 15 |
Let there be a ball of conditional color, such that the conditional colored ball gains the same color as that of the color of a ball it is paired with - or, if drawn alone or grouped with two or more other balls of different colors or only conditional colors, it is black.

In such a jar of colored balls where the balls are either red, black or of conditional color, where there is a 50% chance that the two balls randomly taken out of the jar will both be red, there could be five balls in the jar (two red and three black [with two of the black being of conditional color]). The total percentage of red balls in the jar -- in this case -- is 40%.

[Minus the possibility of another variant to a ball of conditional color, the smallest number of colored balls in the jar where there is a 50% chance that the two balls randomly taken out of the jar will both be red is 75% (four balls - three red and one of a non-red, non-conditional color).]

  Posted by Dej Mar on 2011-09-13 03:24:48
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