请教Prep数学

allieh

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

A.    Statement 1 ALONE is sufficient, but statement 2 alone is not sufficient.
B.    Statement 2 ALONE is sufficient, but statement 1 alone is not sufficient.
C.    Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D.    EACH statement ALONE is sufficient.
E.    Statement 1 and 2 TOGETHER are NOT sufficient.

Answer: C
I chose E


 
In the figure above, points P and Q lie on the circle with center O. what is the value of s?

Answer: s=1

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the present change in the concentration of chemical A required to keep the reaction rate unchanged?

a. 100% decrease
b. 50% decrease
c. 40% decrease
d. 40% increase
e. 50% increase


If x>y^2>z^4, which of the following statements could be true?
1. x>y>z
2. z>y>x
3. x>z>y

a. 1 only
b. 1 and 2 only
c. 1 and 3 only
d. 2 and 3 only
e. 1, 2 and 3

Answer e
I chose c because I cannot find any example proving 2 is right.
When x=36, y=+/-5, and x=+/-2, 1 and 3 are true but 2.



A certain stock exchange designates each stock with a one-, two-, or three-letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order constitute a different code, how many different stocks is it possible to uniquely designate with these codes?

Answer 18,278


If s and t are two different numbers on the number line, is s+t equal to 0?
1) the distance between s and 0 is the same as the distance between t and 0
2) 0 is between s and t.
A.    Statement 1 ALONE is sufficient, but statement 2 alone is not sufficient.
B.    Statement 2 ALONE is sufficient, but statement 1 alone is not sufficient.
C.    Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D.    EACH statement ALONE is sufficient.
E.    Statement 1 and 2 TOGETHER are NOT sufficient.
Answer: A
I chose C because I thought there were two possibilities, when s=t and s=-t.


谢谢大家讲解！！

[此贴子已经被作者于2008-12-29 9:27:12编辑过]

allieh

有没有人帮我看看阿~