[求助]GWD 涛涛 15-28

Q28:B?????

A school administrator will assign each student in a group of n students to one of m classrooms.  If 3 < m < 13 < n, is it possible to assign each of the n students to one of the m classrooms so that each classroom has the same number of students assigned to it?

(1)   It is possible to assign each of 3n students to one of m classrooms so that each classroom has the same number of students assigned to it.

(2)   It is possible to assign each of 13n students to one of m classrooms so that each classroom has the same number of students assigned to it.

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.

这题怎解？？？答案是B。

Answer:

对的阿

因为m<13，所以13/m不可能是整数，而要求13n/m是整数，所以n/m必须整

嗯

同意楼上分析，

但这题问is it possible？使我选D。感觉DS题这样问法很怪！

题问N人能否均分到M班。实质是问：N是不是M的倍数？

结合题意（M=4or5or6or7or8or9or10or11or12）,可知该题在问：N是不是4、5、6、7、8、9、10、11、12的公倍数？

4=2*2

5

6=2*3

7

8=2*2*2

9=3*3

10=2*5

11

12=2*2*3

可知，4、5、6、7、8、9、10、11、12的最小公倍数为2*2*2*2*3*3*5*7*11。

如3N能被4、5、6、7、8、9、10、11、12整除，则N=2*2*2*2*3*5*7*11。N不能被M整除。（1）不充分。

如13N能被4、5、6、7、8、9、10、11、12整除，则N=2*2*2*2*3*3*5*7*11。N能被M整除。（2）充分。