If n and p are integers, is p>0?
1) n+1 >0
2) np>0
1) insuff b/c not enough info
2) insuff b/c n and p could both be positive or both be negative
1+2) I thought it was insufficient b/c if n+1>0, n has to be negative. so that means p has to be negative to make the question sufficient. Or is this the type of question where "NO" is sufficient?
GMAT Forum
3 postsPage 1 of 1
- thisSunday
- Guest
The statement states that n and p are both integers.
From statement 1, we can conclude that n+1>0 => n> -1 => n = 0, 1, 2, etc. However this is insufficient info to answer the question.
From statement 2, we know that np>0 => n & p have the same sign, but don't know which sign. We can also conclude that their product is not 0.
Statement 1 & 2 together: n> -1 and np> 0, we know that n can't be 0, but it's a positive integer, so p is also positive.
Hope this helps.
From statement 1, we can conclude that n+1>0 => n> -1 => n = 0, 1, 2, etc. However this is insufficient info to answer the question.
From statement 2, we know that np>0 => n & p have the same sign, but don't know which sign. We can also conclude that their product is not 0.
Statement 1 & 2 together: n> -1 and np> 0, we know that n can't be 0, but it's a positive integer, so p is also positive.
Hope this helps.
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
The guest answer here is good.
Careful with the inequalities; you interpreted n+1>0 as meaning that n is a negative number, which is almost the exact opposite of what that inequality actually means (see the guest solution for the correct interpretation). Interestingly, you correctly interpreted np>0, an inequality that gives many people a headache.
Lesson to take away here: If you see an inequality involving ONE variable, then SOLVE for the variable, rather than thinking in terms of positive, negative, etc. Those concepts are useful for TWO-variable inequalities (like np>0).
Careful with the inequalities; you interpreted n+1>0 as meaning that n is a negative number, which is almost the exact opposite of what that inequality actually means (see the guest solution for the correct interpretation). Interestingly, you correctly interpreted np>0, an inequality that gives many people a headache.
Lesson to take away here: If you see an inequality involving ONE variable, then SOLVE for the variable, rather than thinking in terms of positive, negative, etc. Those concepts are useful for TWO-variable inequalities (like np>0).
3 posts Page 1 of 1