GWD 几道数学题，谢谢大侠们！

jiubuxihuan

1 投硬币，a certain coin has equal probobility of landing on either side, if the coin is tossed 3 times, what is hte probobility that is will land on the same side each time?

a 1/8   b 1/4 c 1/3 d 3/8 e 1/2            答案是b 我怎么觉得是a呢？

2 Is the decimal represataion of X where 0<x<1 is the tenths digit of x nonzero?

1)16x is an integer

2)8x is an integer

3 What is the madian number of employees assigned per project for the porjects at company z?

1)25 percent of the projects at company z have 4 or more employees assigned to each project

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

many thanks for Daxia!

joanrain

以下是引用jiubuxihuan在2005-11-3 1:10:00的发言：

1 投硬币，a certain coin has equal probobility of landing on either side, if the coin is tossed 3 times, what is hte probobility that is will land on the same side each time?

a 1/8   b 1/4 c 1/3 d 3/8 e 1/2            答案是b 我怎么觉得是a呢？

有两种情况啊：正正正，反反反，所以应该是2/8＝1/4

2 Is the decimal represataion of X where 0<x<1 is the tenths digit of x nonzero?

1)16x is an integer

2)8x is an integer

把1分别除以16和8，得到0.0625和0.125，所以16x是整数的话，十位数有可能是0也有可能是其他数，但是8x是整数的话，十位数只能是非零了，等于0的话x就超过了所给出的范围

3 What is the madian number of employees assigned per project for the porjects at company z?

1)25 percent of the projects at company z have 4 or more employees assigned to each project

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

25％   40％   35％ 那么median只能在40％人中啦

然后25％是大于等于4，35％是小于等于2，所以40％的人只能是3，不会是3个半人，咔咔

many thanks for Daxia!

：（ 55，我是小虾……

jiubuxihuan

第三题还是不懂：为什么median只能在40%呢？如果40%的porjects have 6 or more people 那么就会有不同的结果了阿，所以结果不唯一阿？

ylpurcahse

条件1说了4 or more了，所以你说的“6 or more people"这种情况就已经包括在里面那25%里面了。所以median那40%一定在2-4里，就是3