麻烦求解

scholar

各位NN看几道数学 谢谢
For a convention, a hotel charges a daily room rate of $120 for 1 person and x dollars for each additional person.What is the charge for each additional person?

(1)The daily cost per person for 4 people sharing the cost of a room equally is $45.

(2)The daily cost per person for 2 people sharing the cost of a room equally is $25 more than the corresponding cost for 4 people. D





A photographerwill arrange 6 people of 6 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 6 people are possible?



A.5

B.6

C.9
D.24
E.36
A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster.If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?



A.0
B.1/9
C.2/9

D.1/3
E.1

catharine6699

第一题：（1）120+3x=45*4
             (2)  (120+x)/2=25+(120+3x)/4  
单独都行

catharine6699

假设高度为123456，先可以确定1在第一排左一,  6在第二排右三，然后开始讨论，若5在第二排的左二，则剩下的有2种情况；若4在第二排的左二，则剩下的有2种情况；若3在第二排的左二，则剩下的只有1种，即2在第二排的左一，45分别在第一排的二三。    这道题只能分情况考虑哦！

fwj34

第二题我用枚举的。。。最高的必须在第二排最右边，最矮的必须在第一排最左边，后面就枚举了。。。

fwj34

第三道可以这么理解：
坐第一辆车的可能是1/3,第二次选择中不能坐第一辆车的可能是1－1/3＝2/3,第三次坐第三辆车的可能有是1/3，然后这三辆车的顺序可以随意改变：×3，结果就是2/9 了

catharine6699

第三题是：分母为3*3*3 分子为p三三，就相当于是3个车排列，看有多少排法就行了啊