Each of the 25 balls in a certain box is either red, blue,

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Each of the 25 balls in a certain box is either red, blue, [#permalink]

05 Feb 2009, 05:24

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Each of the 25 balls in a certain box is either red, blue, or white and has a number from 1 to 10 painted on it. If one ball is to be selected at random from the box, what is the probability thath the ball selected will either be white or have an even number painted on it?

1) The probability that the ball will be both white and have and even number painted on it is 0

2) The probability thath the ball will be white minus the probability thath the ball will have an even number painted on it is 0.2

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Re: DS probability [#permalink]

05 Feb 2009, 08:21

From stmt1: p(W) intersection p(E) = 0

Hence, p(WUE) = p(W) + p(E)

From stmt2: p(W) - p(E) = 0.2

Even combining two statemement, we are not able to find out p(W) + p(E).

Hence, E.

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Re: DS probability [#permalink]

05 Feb 2009, 08:49

scthakur wrote:

From stmt1: p(W) intersection p(E) = 0

Hence, p(WUE) = p(W) + p(E)

From stmt2: p(W) - p(E) = 0.2

Even combining two statemement, we are not able to find out p(W) + p(E).

Hence, E.

Thanks, this is what I did: from statement one we know that there are no even white balls, so if p(w) -p(e) = 0.2, then p(w) - 0 = 0.2 so p(wUe) = 0.2 I have assumed that there are balls of the three colors, thus necessarily leading stmt1 to conclude that there are no even white balls. Did I get it wrong because there might be no white balls at all ("either white, or red or blue")?

Re: DS probability [#permalink] 05 Feb 2009, 08:49

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Each of the 25 balls in a certain box is either red, blue,

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Each of the 25 balls in a certain box is either red, blue,

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