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If p<q and p<r, is pqr<p? (1) pq<0 (2) pr<0 [#permalink]
16 Jul 2007, 19:22
Question Stats:
47% (02:19) correct
52% (00:32) wrong based on 2 sessions
OPEN DISCUSSION OF THIS QUESTION IS HERE: if-p-q-and-p-r-is-pqr-p-1-pq-0-2-pr-126285.htmliamba wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0
a) (p)(q)(r) < p b) (p)(q)(r)/p < p/p c) (q)(r)<1 rephrased: if p<q and p<r is (q)(r)<1 1) we know that p or q is negative. this tells us nothing about whether q*r < 1 2) same thing here. 1 and 2 together still tells us nothing. 1 and 2 tells us that p is -ve but doesn't tell us whether q or r is 0. I get E
Last edited by Bunuel on 28 Jan 2012, 03:56, edited 4 times in total.
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1. pq < 0
with p<q, p is neg and q is positive, no info about r (r can be either positive or negative), therefore insuff.
2. pr<0
with p<r, p is neg and r is positive, no info about q (q can be either positive or negative), therefore insuff.
1+2. pq<0 and pr<0, making p negative and both r & q positive, however if p = -1 and q and r both = 1, then (p)(q)(r) = p, therefore insuff.
(E)
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iamba wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0
Stmt1: pq < 0
p < 0 and q > 0
as q < r, so r > 0
But we can't say pqr < p , as p, q and r can be the fractions.
So insuff
Stmt2:
pr < 0
p < 0 and r > 0
we don't know whether q < 0 or > 0
But we can't say pqr < p ,
INSUFF
Taking them together:
Still INSUFF
Hence 'E'
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Re: MGMAT DS Problem [#permalink]
03 May 2008, 16:07
Answer is C
Explanation : p<q and p<r and we need to find if pqr<p
Statement 1 : pq<0 means both have opposite signs and therefore p must be -ve and q must be +ve as p<q as given pqr depends on sign of r. If r is +ve pqr<p If r is -ve pqr>p NOT SUFFICIENT
Statement 2 : pr<0 . As above both must have opposite signs and p must be negative and r must be +ve as p<r given again we cannot determine pqr<p as if r is +ve its true if r is -ve its not. NOT SUFFICIENT
Both together
pq<0 and pr<0 , therefore p is _ve q and r +ve which means pqr is negative but product will be less than p
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Re: MGMAT DS Problem [#permalink]
03 May 2008, 22:34
seongbae wrote: if p is -2 and q and r are both 1, then pqr=-2 which is equal to p. so shouldn't the answer be e? The question asks if pqr < p or not, so all you need to know is yes/no. If pqr = -2 and p = -2, the answer will just be no, and solves the question.
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Re: MGMAT DS Problem [#permalink]
03 May 2008, 23:49
jbpayne wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0
Does anyone have a quicker method to determine positives and negatives? I can get this one right, but it just takes me too long. E. if q=r=1,any -ve value for p makes p = pqr.
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Re: MGMAT DS Problem [#permalink]
04 May 2008, 07:37
GMAT TIGER wrote: jbpayne wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0
Does anyone have a quicker method to determine positives and negatives? I can get this one right, but it just takes me too long. E. if q=r=1,any -ve value for p makes p = pqr. The poster a few posts above you proved that C is sufficient to prove that p is NOT greater than pqr. This always confuses me too, but a DS-type question doesn't ask if the statement p > pqr is true; it asks if we can figure out, in all cases, whether it is true or it is false.
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Re: MGMAT DS Problem [#permalink]
04 May 2008, 09:42
getting E
Each statement individually doesn't give information about the third variable. So they are insufficient individually.
Combined... two scenarios to consider
if p < 0, then q,r > 0 => pqr < p (-ve on both sides) if p > 0, then q,r < 0 => pqr > p (+ve on both sides)
So insufficient.
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nirimblf wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0 1 & 2) tells me that q > 0 and r > 0 but we don't know whether both q and r greater than 1 or whether both are fractions. So, E.
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answer E for me as well.
I wrote an eq'n: p(qr-1) < 0 ... so either p<0 and qr>1 or p>0 and qr<1
from stat 1, i know that p<0 and q>0, since p<q, but i dont know anything about r to see if it satisfies whether qr>1. insuff
from stat 2, i know that p<0 and r>, but nothing about q to see if qr>1 ... insuff.
together, all i know is that q and r are positive, but they could both be fractions, i.e. qr <1, or they could be whole numbers so that qr>1
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yeah I get E..too
p<q, q<r given..pqr<p?
1) pq<0
clearly p<0 q>0..could be 1/2 or 2 etc; however dont know about r..insuff
2) pr<0 clearly p<0 r>0 could 1/2 or 2..dont know anything about q..insuff
together we know that q*r is POSITIVE.. p(q*r)<p?
well if q, r=2 then and say p=-2 the -2*2<-2 YES but if q, r=1/2 and p=-2 the -2(1/4)>-2 NO..
INSUFF E it is
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dancinggeometry wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0 1) p is -ve and q is +ve r can be -ve or +ve insuffcient -- multiple solutions possible 2)p is -ve and r is +ve q can be -ve or +ve insuffcient -- multiple solutions possible combined p -ve and q and r are postive. insuffcient. qr <1 or >1 two solutions possible. pqr<p or pqr>p E
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dancinggeometry wrote: If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0 (2) pr < 0 from 1 ) there are 2 cases p and q have opposite signs. p has to be -ve in order to satisfy inequality p< q -ve * +ve * r < -ve if r is positive this will be true but we dont know anything abt r. so insuff. from 2) p and r have opposite signs. p has to be -ve in order to satisfy inequality p< r -ve * q * +ve < -ve if q is positive this will be true but we dont know anything abt q. so insuff. together we know that q and r are positive. -ve * +ve * +ve < -ve sound suff, but what if p and q are fractions - 0.25 * 0.1 * 0.2 is not less than -0.25 so insuff. E
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I think It is C.
I am agree with that Options A and B are not possible.
Let's combined both options
we have pq < 0 and pr < 0 .
this possible only when p is negative and q and r are positive.
Also, p, q and r are not zero either.
so, (p) (q) (r) < p. It is sufficient to say that it is pqr are always less than p. So answer is C.
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Twoone wrote: I think It is C.
I am agree with that Options A and B are not possible.
Let's combined both options
we have pq < 0 and pr < 0 .
this possible only when p is negative and q and r are positive.
Also, p, q and r are not zero either.
so, (p) (q) (r) < p. It is sufficient to say that it is pqr are always less than p. So answer is C. As x2suresh has explained, since p < 0, if qr >1 then pqr < p. However, if 0 < qr < 1 then pqr > p....hence, C cannot be the answer.
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scthakur wrote: Twoone wrote: I think It is C.
I am agree with that Options A and B are not possible.
Let's combined both options
we have pq < 0 and pr < 0 .
this possible only when p is negative and q and r are positive.
Also, p, q and r are not zero either.
so, (p) (q) (r) < p. It is sufficient to say that it is pqr are always less than p. So answer is C. As x2suresh has explained, since p < 0, if qr >1 then pqr < p. However, if 0 < qr < 1 then pqr > p....hence, C cannot be the answer. C is not correct, take p = -6, q = 1, r = 1, S1 and S2 are met, and stem is also met. -> -6x1x1 is not < -6
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pqr can be less than p only if p is negative and pq positive, so, p and q must be both either positive or negative
1) pq < 0 => p < 0, q > 0, but we don't know whether r is also positive. Ex: p=-2, q=2, r=1, or p=-2, q=2, r=-1. Insuff. 2) The same, Insuff
Together, qr > 0, Suff
C
Last edited by atletikos on 27 Nov 2008, 03:06, edited 1 time in total.
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OA is E from MGMAT
Here's OE they provide.
The question tells us that p < q and p < r and then asks whether the product pqr is less than p. Statement (1) INSUFFICIENT: We learn from this statement that either p or q is negative, but since we know from the question that p < q, p must be negative. To determine whether pqr < p, let's test values for p, q, and r. Our test values must meet only 2 conditions: p must be negative and q must be positive. p q r pqr Is pqr < p? -2 5 10 -100 YES -2 5 -10 100 NO
Statement (2) INSUFFICIENT: We learn from this statement that either p or r is negative, but since we know from the question that p < r, p must be negative. To determine whether pqr < p, let's test values for p, q, and r. Our test values must meet only 2 conditions: p must be negative and r must be positive. p q r pqr Is pqr < p? -2 -10 5 100 NO -2 10 5 -100 YES If we look at both statements together, we know that p is negative and that both q and r are positive. To determine whether pqr < p, let's test values for p, q, and r. Our test values must meet 3 conditions: p must be negative, q must be positive, and r must be positive. p q r pqr Is pqr < p? -2 10 5 -100 YES -2 7 4 -56 YES At first glance, it may appear that we will always get a "YES" answer. But don't forget to test out fractional (decimal) values as well. The problem never specifies that p, q, and r must be integers. p q r pqr Is pqr < p? -2 .3 .4 -.24 NO Even with both statements, we cannot answer the question definitively. The correct answer is E.
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Re: If p < q and p < r, is (p)(q)(r) < p? (1) pq < 0 [#permalink]
27 Jan 2012, 20:07
+1 E Don't forget that q and r can be fractions (0 < q,r < 1) That possibility lower the value of p.
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If p < q and p < r, is pqr < p?Given: p<q and p<r. Question: is pqr<p? --> is p(qr-1)<0? (1) pq < 0 --> p and q have opposite signs, as given that p<q then p<0 and q>0 --> as p<0 then the question becomes whether qr-1>0 (in p(qr-1) first multiple is negative - p<0, so in order the product to be negative second multiple must be positive - qr-1>0) --> is qr>1? We know that q>0 but all we know about r is that p<r. Not sufficient. (2) pr < 0 --> the same here: p and r have opposite signs, as given that p<r then p<0 and r>0 --> as p<0 then the question becomes whether qr-1>0 --> is qr>1? We know that r>0 but all we know about q is that p<q. Not sufficient. (1)+(2) we have that: p<0, q>0 and r>0. Again question becomes: is qr>1? Though both q and r are positive their product still can be more than 1 (for example q=1 and r=2) as well as less then 1 (for example q=1 and r=\frac{1}{3}) or even equal to 1. Not sufficient. Answer: E. OPEN DISCUSSION OF THIS QUESTION IS HERE: if-p-q-and-p-r-is-pqr-p-1-pq-0-2-pr-126285.html
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