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158. 15810-!-item-!-187;#058&010518 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.
答案是c，
192. 18939-!-item-!-187;#058&011984 Of the 75 houses in a certain community, 48 have a patio. How many of the houses in the community have a swimming pool?
(1) 38 of the houses in the community have a patio but do not have a swimming pool.
(2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio.
答案是B
又是概率头疼啊 | 
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发表于 2008-7-12 15:42:00
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