[求助]GWD 第一套中，好几道弄不懂啊

yang8630

    

Q2:
        （E）

    

If 2 different representatives are to be selected at random
from a group of 10 employees and if p
is the probability that both representatives selected will be women, is p > 1/2?

    

(1)
          More than 1/2 of the 10 employees
are women.

    

(2)
          The probability that both
representatives selected will be men is less than 1/10.

    

                  

    

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. Statements (1) and (2) TOGETHER are NOT
sufficient.

    

 

    

                               

    

Q8:
        （D）

    

The points R, T, and U lie on a circle that has radius 4.  If the length of arc RTU is 4pie/3, what is the length of line segment RU?

    

 

    

A.    4/3

    

B.     8/3

    

C.     3

    

D.    4

    

E.     6

    

 

    

Q10:
        （C）

    

What is the value of (x
- y)⁴?

    

(1)
          The product of x and y is 7.

    

(2)
          x and y are integers.

    

                  

    

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. Statements (1) and (2) TOGETHER are NOT
sufficient.

    

 

    

 

    

Q17:（D）

    

If x, y, and k are positive numbers such that 10[x/(x+y)] + 20[y/x+y] = k and if x < y, which of the following could be the value of k?

    

 

    

A.    10

    

B.     12

    

C.     15

    

D.    18

    

E.     30

    

 

    

Q26:
        （A）

    

If the units digit of the three-digit positive integer k is nonzero, what is the tens digit of k?

    

(1)
          The tens digit of k + 9 is 3.

    

(2)
          The tens digit of k + 4 is 2.

    

                  

    

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. Statements (1) and (2) TOGETHER are NOT
sufficient.

[此贴子已经被作者于2008-10-13 6:00:07编辑过]

xiaoy791

Q2:假设x women，p=x(x-1)/10(10-1)(排列组合，C  不知怎么书写)是否大于0.5，即x(x-1)>45?

(1) More than 1/2 of the 10 employees are women. x at least is 6,and at most 10,代入上式，x为6 or 7时，上式<45,为8，9or10时，大于45；

(2)The probability that both representatives selected will be men is less than 1/10. 假设men 为y，p'=y(y-1)/10(10-1)<1/10,即

y(y-1)<9,则y为1，2或3，则x可为9，8or7，代入（1），也不能确定

联合（1），（2），也不能确定。

Q8：the perimeter of the circle is 8pie,so the ratio the length of arc RTU  to the perimeter is 4pie/3/8pie=1/6.Then the central angle is 60degree.构建三角形ORU，为等边三角形，所以RU＝radius＝4

Q10：很显然，1和2 单独都不行，但结合起来的话，由于x and y are integers,but xy=7,so x and y can be 1,7,-1,-7,代入(x - y)⁴

值均为6⁴

Q17：10[x/(x+y)] + 20[y/x+y]＝10[(x+y)/(x+y)] + 10[y/x+y]＝10+ 10[y/x+y]，由于x, y are positive numbers andx < y，so 1/2<y/x+y<2,5<10[y/x+y]<10,则 15<k<20, and only 18 is in the range

Q261)The tens digit of k + 9 is 3 and the units digit of the three-digit positive integer k is nonzero,so the units digit ranges 1 from 9.k + 9后使得units digit大于10，进一位，故the tens digit of k is 2

（2）按照同样分析，当个位小于6时，k＋4后不进位，当个位大于等于6时进一位，故不能确定