[求助] 三道数学题，两道关于排列组合PS， 一道是有关中位数的DS

PS 1: A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any one of the three cars . each time that passengers rides the roller coaster, if a certain passenger is to ride the roller coaster three times, what is the probability that the passenger will ride in each of the 3 cars?

我一看题目，觉得好象不难，就是说这个passenger三次要做三个不同的cars，于是我的答案是1/9， 但是正确答案是2/9, 我遗漏了什么地方吗？

PS2:  A photographor will arrange six people of six different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row. The heights of the people within each row must increase from left to right and each person in the second row must be taller than the person standing in front of him or her, how many such arrangements of the six people are possible?

我觉得就是按照6个人的高矮排序，应该就只有一种，我想知道大家对于这道题是怎样思考的？

DS: Which is the median number of employees assigned per project for the projects at company Z?

(1) 25 percent of the projects at company Z have 4 or more emplyees assigned to each project

(2) 35 percent of the projects of company Z have 2 or fewer employees assigned to each project

如果公司的总人数未知，应该是无法知道median的，我可能对题目的理解还存在问题。

谢谢大家的解答！

答案：PS1 是 1/9

      PS2 是 5种

      DS  是 C

请大牛们解释一下，本人非常感激

不好意思，PS1正确答案是2/9, 我认为是1/9

麻烦大家解释

谢谢

谢谢“站在一楼跳楼”

PS1，PS2想明白了

DS我知道我的问题了，我还是没有把题目意思明白，我一直把两个statements割裂，即使在做both考虑的时候，我也是陷入了惯性思维，总是想一个25percent 一个 35percent，怎么可能知道median，如果这道提后一个statement是小于30percent的话，应该就是E了。

呵呵，开个玩笑，做DS的时候，好象总是处在“精神分裂”的边缘，一会儿分开考虑，一会儿集中思考

很有意思

谢谢

lz，第一题答案到底是1/9还是2/9啊？

怎么解？