prep1-158

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.

E

请教思路，谢谢~~

不是牛人，一起探讨！

试想条件1， 只要是白的，一定写着奇数，但没说25个球几个白的，几个奇数，所以不行

试想条件2，是白球的可能性减去是偶数的可能性是0.2，同样，因为对白球数量与奇数偶数球数量没有限定，所以也无用。