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题库 / Prep2007E1-DS-147
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.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
问题问的是D的人数比例。
1）M的平均工资比所有人的平均工资少5000。单条件显示不行。
2）D的平均工资比所有人的平均工资多15000。同上，单条件显示不行。
both的话，假如平均工资是x，每个M对平均工资的贡献值是-5000，每个D对平均工资的贡献值是+15000，所以显然3个M对应一个D，所以是可以算出比例来的。
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