Q21:

Harvey teaches a certain number of biology students in 2 classes, K and L. He can divide the students in class K into 7 groups of n students each. He can divide the students in class L into 6 groups of p students each with 1 student left over. How many students are in class L ?

(1) n = p

(2) There are 5 more students in class K than in class L.

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: c

但是我觉得光B就可以满足了 难道一定要n＝p

7n=6p+1+5=6(p+1)

满足该条件的n,p太多啦,所以要限制一下才有且仅有一个答案;选C

同意C.

开始一看这个题的时候也觉得B就可以了.

7n=6p+1+5=6(p+1)满足这个的整数很多,比如n=6.p+1=7;n=12,p+1=14...都是可以的.

所以需要限制.

同意C

但不知道大家怎样理解题目中

He can divide the students in class L into 6 groups of p students each with 1 student left over

我以为是每个班级在分组后都余下一人，

7n+1=6p+1+5

n=5, p=5

K=7n+1=36 L=6p+1=31

嗯，终于明白自己错在那里了。。