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

I got this wrong, because I missed the point that n & p are integers.

Anyways, here's the correct solution.

1. n + 1 > 0. This means that n > -1. Insufficient
2. np > 0 We have no information about n, so can't conclude whether p is is positive or not.

Combining 1 & 2.

Since n & p are integers, thus n = {0, 1, 2, 3....}
np > 0 so, n has to be more than 0 {1, 2, 3....}

So, for the product to be positive, p has to be positive.

So, answer should be C

n & p are integers, sorry, caught my mistake, easy question.

1. insuff, no info about p
2. insuff, n and p can be either both positive or both negative

together from I n>-1 so n >= 0
so n is either zero or positive
and from II we know is not zero so p>0

So C.

Easy C... Doesnt matter whether a,p are integers are not!

1) n > -1. No idea about p. Insufficient.
2) np > 0. Suggest both n and p are negative, or both n and p are positive. Insufficient.

Using both, we know n is negative, so p must be negative.

Ans C

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

(1) n + 1 > 0
(2) np > 0

Ans should be E...

Clearly 1 and 2 are both insufficient.

Taken together,
1 says n>-1 ... So n can be zero.
and in 2 np can be 0 too... so its not sufficient.

Can I please have an ansewr to this?

Thanks

Oh god... Its the answer, sorry greatly confused... As I am new to this kind of questions.

This is a question that appears in PREP. There are 2 variables (n and p). In order to match the number of variables to the number of equations, we need 2 equations. Since the condition 1) and the condition 2) each has 1 equation, there is high chance that C is the correct answer. Using both the condition 1) and the condition 2), we get n=1,2,3....>0. Then, p also becomes positive. The answer is yes and the condition is sufficient. Thus, the correct answer is C.

- For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
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This is a really easy question but could not hold on to my temptation of penning down the solution.
we know n and p are integers so they can be 0 or + or -ve.

now 1) n+1>0
hence n>-1
n =0, 1 , 2 etc thus N is positive but no info about P insuff

2) NP>0
which means both and n and p has same sign but no info about the sign
insuff

combining we have n>0 and n and p have same sign so p is positive
suff

Let's consider (1) N+1 >0. This clearly tells you nothing about p, so is insufficient by itself, ruling out A&D.

Let's look at (2). np >0. This tells us that n,p and either both positive or both negative. Therefore it is insufficient to answer whether p >0, so we can eliminate B.

Now let's consider (1) and (2) together. (1) combined with the fact that N and P are integers tells us that N>= 0. (2) tells us that N and P are either both positive or both negative and that neither are equal to 0. Combined with (1) we therefore know what N is positive, and from (2) P must be positive too. So (1) and (2) together are sufficient and the answer is C.
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Given: n and p are integers

Target question: Is p > 0?

Statement 1: n + 1 > 0
No information about p.
Statement 1 is NOT SUFFICIENT

Statement 2: np > 0
There are several values of n and p that satisfy statement 2. Here are two:
Case a: n = 1 and p = 1. In this case, the answer to the target question is YES, p is greater than 0
Case b: n = -1 and p = -1. In this case, the answer to the target question is NO, p is NOT greater than 0
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that n + 1 > 0
This means n > -1
Since n is an integer, we know that the possible values of n are: 0, 1, 2, 3, 4, 5, 6, . . .

Statement 2 tells us that np > 0
Since np is greater than 0, we know that n ≠ 0. So, now the possible values of n are: 1, 2, 3, 4, 5, 6, . . .
In other words, we can be certain that n is POSITIVE
If n is POSITIVE AND np > 0, we can be certain that p is POSITIVE
So, the answer to the target question is YES, p is greater than 0
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent
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