求助~！2道prep的数学题

1. If n and p are positive integers, is p>0?

(1) n+1>0

(2) np>0

答案：both together are sufficient

2. 72% of the male students and 80%of the female students have applied to college. What fraction of the students in the class are male?

(1) There are 840 students in the class

(2) 75% of the students in the class have applied to college

答案：（2）alone is sufficient.

多谢帮忙啦~~

2）根据条件2

男X 女Y

72%*X+80%*Y=75%(X+Y)

x/x+y=5/8

咋感觉第一题不对劲呢~~~

前面给了条件说都是positive integers，怎么后面还问p是不是正数呢？

我错了。。。

If n and p are integers, is p>0?

(1) n+1>0

(2) np>0

答案： both together are sufficient

题目说了是整数，

1：N大于-1，那N必然大于0

2：NP大于0, N,P同正，同负

1+2，得出P大于0，接出，所以应该是C