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Number Comparison Problem

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Number Comparison Problem

by vongdn » Tue Oct 05, 2010 9:03 pm
If N and P are integers, is P > 0 ?

(1) N + 1 > 0
(2) NP > 0


I see that (1) is insufficient.

Wouldn't (2) be sufficient though? Cause you would divide both sides of the statement by N and P > 0 right? Or is that wrong?

The answer is that Both together is sufficient, but I don't see it.
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by shovan85 » Tue Oct 05, 2010 10:12 pm
(2) will not be sufficient.

Because NP > 0 then you cannot divide both sides with N.

We know +ve * +ve = +ve and _ve * -ve = -ve.

If NP > 0 then either N and P both greater than zero or both less than zero.

However if you combine both then you are sure N > 1 from (1) so N is +ve. Hence P must be +ve.

IMO C
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by neerajkumar1_1 » Tue Oct 05, 2010 10:16 pm
question is asking whether P is +ve or P>0

statement 1) N +1 > 0
nothing abt P, this insufficient

statement 2) NP > 0

when product of 2 integers is +ve, this means that either both are positive or both are negative
since P can be both +ve and -ve, statement 2 is insufficient.

together,
N > -1
and NP >0
since N is an integer N >=0

since the product NP>0
hence N will be +ve,
since N is +ve, P will have to be +ve
Hence, sufficient.

IMO: C

to answer your question, u should be careful when dividing both side by N with inequalities... since u dont know whether N is +ve or -ve

Ur calculation is fine, but u r assuming N is +ve...
but u should consider both..
so in this case...
if N is +ve
P > 0 or +ve
but if N is -ve
P<0 or -ve

I would suggest that you revise ur inequalities a bit more...

Hope this helps!!!
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by shovan85 » Tue Oct 05, 2010 10:45 pm
shovan85 wrote:
However if you combine both then you are sure N > 1 from (1) so N is +ve. Hence P must be +ve.

IMO C
Sorry I made a mistake....N>-1 :)
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by blaster » Wed Oct 06, 2010 1:22 am
i think , key point here is N>-1 , so N is positive (statement 1) .
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by shovan85 » Wed Oct 06, 2010 4:54 am
blaster wrote:i think , key point here is N>-1 , so N is positive (statement 1) .
N > -1 does not necessarily makes N is +ve. It can be negative fractions or zero.
As NP>0 we cannot take n=0.
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by Yanat » Wed Oct 06, 2010 7:42 am
IMO the answer is C.
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