prep两题

Each employee on a certain task force is either a manager or a director.What percentage of the employee on the task force are directors?
(1)The average salary of the managers on the task force is $5,000 less than the average salary of all employee on the task force.
(2)The average salary of the directors on the task force is $15,000 greater than the average salary of all employee on the task force.

答案是C,不明白..我觉得算不出来啊

On a certain sight-seeing tour,the ratio of the number of women to the number of children was 5 to 2.What was the number of men on the sight-seeing tour?
(1)On the sight-seeing tour,the ratio of the number of children to the number of men was 5 to 11.
(2)The number of women on the sight-seeing tour was less than 30.

答案C,(2)并没有给出WOMEN数啊..怎么得出MEN数的?

1，设M,D分别有x,y人，求X/Y，设平均A

（A-5000）x+（A+15000）y=A(x+y) à15000y=5000x

1) C：M=5：11

2）W 少于30，为5倍数

      设为25，C为10，M为22 一组

              设为20，C为8，M为88/5

              设为15，C为6，M为66/5

              设为10，C为4，M为44/5

              设为5，C为2，M为11/10

如此只有第一组满足。

W:C=5:2; C:M=5:11;

W:C:M=5:222/5) 所以W=5k, C=2k, M=(22/5),所以k是5的倍数,

又k<6 所以k=5，所以M=22

W:C=5:2; C:M=5:11;

W:C:M=5:222/5) 所以W=5k, C=2k, M=(22/5)k, 所以k是5的倍数,

又k<6 所以k=5，所以M=22

恩..懂啦

谢谢大家