[求助]请教几道GWD数学题

Q23:

In the decimal representation of x, where 0 < x < 1, is the tenths digit if x nonzero?

(1)     16x is an integer.

(2)     8x is an integer.

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.

Answer: B

Q7:

For a certain race, 3 teams were allowed to enter 3 members each.  A team earned 6 – n points whenever one of its members finished in nth place, where 1 ≤ n ≤ 5.  There were no ties, disqualifications, or
            withdrawals.  If no team earned more than 6 points, what is the least possible score a team could have earned?

A.    0

B.     1

C.     2

D.    3

E.     4

Answer:D
                

Q9:

Professor Vasquez gave a quiz to two classes.  Was the range of scores for the first class equal to the range of scores for the second class?

(1)   In each class, the number of students taking the quiz was 26, and the lowest score in each class was 70.

(2)     In each class, the average (arithmetic mean) score on the quiz was 85.

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.

1,（1）由已知得16X大于0小于16，1除以16=0.0625，15除以16=0.9375，所以不能确定小数十位是否为0

（2），同理，1除以8=0.125，7除以8=0.875，其它数都介于上述两者之间，可见小数十位确定都不为0

（2）单独满足条件，选B  

2.一共三组，9个人。因为没有一个队得大于6分，但又必有一个队一名队员第一个完成，所以这个队里的队员完成的顺序一定是第一和第五名及其以后中的某一名。另一个队一定有一个得第二，也就是4分，所以这个队里队员完成的顺序一定是第二，第四名及其以后中的某一名。第三个队就是第三名，3分，加第三名以后的任何两名，所以得分最少也只可能是3分。

3.

第三道题我觉得选E，即使每个class最低分都是70，平均分都是85，参与学生都是26人，也不能保证每个班的分数范围都是一样的。举个例子，第一个班，1个学生70，24个学生85，1个学生100，范围30；第二个班，1个学生70，20个学生85，5个学生88，范围18。比较极端，只是举例~