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[数学] Prep数学第158题编号15810-!-item-!-187;#058&010518

[数学] Prep数学第158题编号15810-!-item-!-187;#058&010518

lzllfz问道:

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 that the ball selected will either be white or have an even number painted on it?

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

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

我认为(2)是可以的 因为可以抽到偶数的概率是可以算出来的 设白球数量是N --------就是 N/25-12/25=0.2 求出N=17然后(17/25)*(12/25)就能够求出来了啊


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这道题做错了,看看解答

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