请教 prep math-189

ypngzhang

189.Each employee on a certain task force is either a manger or a director. What percent of the employees on the task force are directors?

1) The average salary of the mangers on the task force is $5000 less than the average of all employees on the task force.

2) The average salary of the directors on the task force is $15000 greater than the average salary of all employees on the task force.

Ans. C

谢谢！
   

对不起，想把字放大点，死活放不大

[此贴子已经被作者于2007-4-28 18:51:05编辑过]

ypngzhang

为什么没人理呢？

谁教教我吧   送上一块西瓜   + 一杯咖啡

ypngzhang

还是没人理，再冒上来，看看有人帮我么

Elynn_Chen

根据条件，设本组average salary 为x，则根据条件1，2，average salary of manager=x-5,000，average salary of director=x+15,000;

设这一组manager人数为a， director人数为b，提干要求b/(a+b)

列方程：

(x-5,000)*a+(x+15,000)*b=x*(a+b)

打开，两边消掉x*(a+b)，就能求出a/b, 然后求出b/(a+b)

所以选C

ypngzhang

谢谢 Elynn MM, 没想到式子一打开，就可以消掉那些复杂的东东，以为式子很复杂，就敢没去列式子了。看来以后要大胆的列出式子，可能没有想象的那么复杂。

谢谢！！