[求助]GMATprep

1.The residents of town x participated in a survey to determine the number of hours per week each resident spent watching television. The distribtuion of the results of the survey had a mean of 21 hours and a stardard deviation of 6 hours. The number of hours that Pat, a resident of town x, watched television last week was between 1 and 2 standard deviations below the mean. Which of the following could be the number of hours that Pat watched television last week?

a.30  b.20. c. 18. d.12. e. 6

Answer is d. I have no idea about it.

2.Each employee on a certain task force is either a manager or a dirctor. What percent of the employees on the task force are directors?

The aswer is C. My choice is E. Why?

Tks.

Sorry about the No 2, I forgot to put the conditions.

2.Each employee on a certain task force is either a manager or a dirctor. What percent of the employees on the task force are directors?

1, The average salary of managers on the task force is 5,000 less than the average salary of employees on the task force.

2.The average salary of directors on the task force is 15,000 more than the average salary of all employees on the task force.

The aswer is C. My choice is E. Why?

Tks.

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2.Each employee on a certain task force is either a manager or a dirctor. What percent of the employees on the task force are directors?

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

(2) The average salary of directors on the task force is 15,000 more than the average salary of all employees on the task force

没有看懂sunshinerabMM的式子是什么意思？有谁能帮忙解释一下？这道题怎么算出的C