Prep-T1-#147(DS)

[邁向高等學府]

#147
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(arithmetic mean) salary of the mangers on the task force is $5000 less than the average salary of all employees on the task force.

2. The average (arithmetic mean )salary of the mangers on the task force is $15000 greater than the average salary of all employees on the task force.

Ans. C
如何算出的？？煩請版上大大指教…

[Enriqueta]

原本貼的題目(2)有錯
Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?

(1) The average (arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.

(2) The average (arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.

假設director佔全部的比率是D，全部員工平均薪水是X千元
(1)manager的平均薪水是(X-5)千元
(2)director的平均薪水是(X+15)千元

求出公式： D(X+15) +(1-D)(X-5)=X

可以求出D=25%

[hwatai]

不好意思，看不太懂Enriqueta的方法，另外一種比較笨的解法

由於全部員工平均薪水是X千元
(1)manager的平均薪水是(X-5)千元
(2)director的平均薪水是(X+15)千元

令MANAGER人數=M, director人數=D
故M(x-5)+D(x+15)=(M+D)x (即manager總薪水+director總薪水=所有人的總薪水)
xM-5M+xD+15D=xM+xD
15D=5M
3D=M
故D占了總人數25%