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Luci
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Post subject: If mv<pv<0, is v>0?  Posted: Wed Aug 15, 2007 3:01 pm |
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If mv<pv<0, is v>0?
(1) m<p
(2) m<0
GMAT PREP says the correct answer is D. But I thought it was B, I dont understand how 1 makes it sufficient.
(1) m<p and mv<pv<0
if m and p are negative values (ex. m=-5, p=-3) then v must be positive whatever is its value
if m and p are positive values (ex. m=3, p=5) then v must be negative if we have mv<pv<0
if m is negative and p is positive (ex. m=-2, p=3) then it is inconsistent with mv<pv<0
So I dont understand where I making the mistake
(2) m<0 and mv<pv<0
Here if m<0 then if we want mv<pv<0, v must be positive. SUFFICIENT
Thanks
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GMAT 2007
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Post subject: Posted: Thu Aug 16, 2007 11:54 am |
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(1) if m<p, mv<pv<0 will only hold if V is +ve and M and P are -ve. For other two cases that you mentioned mv>pv so they are not valid.
Hence, for mv<pv<0 V to hold, V has to +ve. So (1) is sufficient.
GMAT 2007
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StaceyKoprince
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Post subject: Posted: Sat Aug 18, 2007 3:44 pm |
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| ManhattanGMAT Staff |
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Posts: 6077
Location: San Francisco
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Luci, you were on the right track with your process, but you didn't actually work out the numbers, so you didn't notice that some of them were inconsistent with the given condition (mv<pv<0). I love trying numbers as a technique, but make sure you follow through just a bit more on the calculations.
If you had, you would have seen:
ex. m=3, p=5, and let's make v =-2
mv = -6
pv = -10
-6<-10<0
Which is not true, so that combination is invalid - I can't use it to test the statement. The only way to make it work would be to make p less than m, but statement one gives the condition m<p, so I can't do it.
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Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT
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harshasks
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Post subject: Re: If mv<pv<0, is v>0? Posted: Tue Jul 12, 2011 10:56 pm |
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Easier way to do this is since mv<pv<0 Just take mv<pv => v(m-p)<0 , hence either v<0 or m-p<0 both cannot be true together. Since in A you are given m<p => m-p<0 which makes v +ve always and hence A is sufficient . You know B already.
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RonPurewal
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Post subject: Re: If mv<pv<0, is v>0? Posted: Fri Jul 15, 2011 2:19 am |
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| ManhattanGMAT Staff |
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harshasks wrote: Easier way to do this is since mv<pv<0 Just take mv<pv => v(m-p)<0 , hence either v<0 or m-p<0 both cannot be true together. Since in A you are given m<p => m-p<0 which makes v +ve always and hence A is sufficient . this is correct, although i would take out “easier” and replace it with “different”. (people from different educational backgrounds will have widely differing ideas of what is “easier”.) Quote: You know B already. not sure what this means. if it means “this has already been derived above”, then yes. if it means “this is given in the statement itself”, then, not quite -- you still have to do some mathematics in order to derive it.
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ven2
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Post subject: Re: If mv<pv<0, is v>0? Posted: Tue Jan 03, 2012 3:13 am |
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I worked it out in the following way plug in numbers consider possibility 1) m =3 p=2 v=-5 2) m =-3 p=-2 v=5 both the above possibilities satisfy the equation mv<pv<0 Case 1) m<p so 1 is not possible so v as to be greater than 0 case 2) m<0 so yes only m =-3 p=-2 v=5 holds true D
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jnelson0612
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Post subject: Re: If mv<pv<0, is v>0? Posted: Wed Jan 11, 2012 10:23 pm |
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| ManhattanGMAT Staff |
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Posts: 1857
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Great! Yes, plugging numbers is such a useful way to handle problems such as this one.
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Jamie Nelson
ManhattanGMAT Instructor
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rachelhong2012
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Post subject: Re: If mv<pv<0, is v>0? Posted: Fri Feb 10, 2012 12:13 pm |
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You can also solve this problem without plugging in #'s. I did this problem with flow chart approach learned from advanced quant strategy book. Basically, if I can rephrase the question starting with a condition: that if v is positive, then I can divide v across the board directly. This condition thus leads to two possiblities, one in which: v =pos so it becomes m<p<0 And one in which v= neg in which case m>p>0 (pretending that the scenario is opposite, then I had just flipped the sign by dividing by a neg number, hence I'm compensating it by flipping the sign later. Therefore, we arrived at two different conclusions, based on whether v is positve or negative. (1) m<p this statement tells us that it's the first scenario of m<p<0 in which case v=pos suff (2) m<0 this statement also tells us that it's the first scenario of m<p<0 in which case v=pos suff hence D
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jnelson0612
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Post subject: Re: If mv<pv<0, is v>0? Posted: Sun Feb 12, 2012 12:05 am |
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| ManhattanGMAT Staff |
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Posts: 1857
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Rachel, great work! Thanks!
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Jamie Nelson
ManhattanGMAT Instructor
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shubham_sagijain
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Post subject: Re: If mv<pv<0, is v>0? Posted: Wed Feb 29, 2012 1:44 pm |
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I used the same approach as is used by Rachel...if a guy knows the rules of inequality, it is easier to work out this problem
But, i agree with Stacey that plugging numbers is always the safest bet :)
Thanks,
Shubh
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RonPurewal
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Post subject: Re: If mv<pv<0, is v>0? Posted: Sat Mar 03, 2012 8:38 am |
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Posts: 7146
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the safest bet is to have as many approaches as possible to the problem, without prejudice toward (or against) any particular method.
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