ChaseDream

标题: 数学一道prep题，有点小疑问求大神帮忙！ [打印本页]

作者: pancypx 时间: 2017-8-22 15:50
标题: 数学一道prep题，有点小疑问求大神帮忙！
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e

但是我觉得（2）单独也是可以的吧，主要是我觉得题目没有说清楚 has a number from 1 to 10 是嘛意思，如果是1-10再1-10再1-5涂完25个球，那就可以求出even的概率了吧？

谢谢！！！

作者: 球三乘以三 时间: 2017-8-22 17:39
别想当然啊。题目没说1-10按次序涂，指的是1-10号球都有，如果按照你这种理解，我是不是可以理解成25个球是按照红蓝白的次序涂的？

作者: echorwillow 时间: 2017-10-25 15:07
说不定每个颜色的1-10有重复的呢？比如红色的球就可以都是偶数

欢迎光临 ChaseDream (https://forum.chasedream.com/)