BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

q positive?

Expert replies
Source: — Data Sufficiency |

by shovan85 » Mon Jan 10, 2011 12:33 am
Night reader wrote:Is q positive?

(1) qp^2 is not negative
(2) q^2 is positive
(2) q^2 is positive

q can be both negative and positive.

Not Sufficient.

(1) qp^2 is not negative

When p = 0 then q can be both -ve or +ve.

Not Sufficient.

Combine both: No Use as when p^2 = 0 then p = 0 and we cannot say anything about q.

IMO E
If the problem is Easy Respect it, if the problem is tough Attack it
Join the discussion

by bblast » Mon Jan 10, 2011 2:45 am
I fell for C, but shovan's explanation makes it clear that it should be E ?
Cheers !!

Quant 47-Striving for 50
Verbal 34-Striving for 40

My gmat journey :
https://www.beatthegmat.com/710-bblast-s ... 90735.html
My take on the GMAT RC :
https://www.beatthegmat.com/ways-to-bbla ... 90808.html
How to prepare before your MBA:
https://www.youtube.com/watch?v=upz46D7 ... TWBZF14TKW_
Join the discussion

by shovan85 » Mon Jan 10, 2011 3:04 am
bblast wrote:I fell for C, but shovan's explanation makes it clear that it should be E ?
First look, I was for A. But the question is testing the fundamentals:

When x is non-negative integer that means x can be Zero OR all positive integers.
When x is positive then x cannot be Zero.
If the problem is Easy Respect it, if the problem is tough Attack it
Join the discussion

by aleph777 » Mon Jan 10, 2011 9:02 am
I believe the answer is C.

The wording in the statements is very subtle:

(1) qp^2 is not negative. This means the value could be zero or positive. Whenever you square either a positive or a negative number squared the result is positive number. But we also need to check for zero, and zero squared is zero. So p^2 could be + or 0. And the same goes for q. In order to get a positive number, if p^2 is positive, then q must also be positive. But because we can't rule out a value of qp^2 = 0, q could = 0 or +.

INSUFFICIENT

(2) q^2 is positive. Following the logic of exponents above, a negative or a positive squared creates a positive, so q could either be negative or positive.

INSUFFICIENT

Together, we know qp^2 is not negative and we know that q^2 is positive. Through statement 2 we know that q is not zero, and therefore q must be a positive number in order to make statement 1 true.

Thus, the answer is C.
Join the discussion

by bblast » Mon Jan 10, 2011 9:44 am
aleph777 wrote:I believe the answer is C.

The wording in the statements is very subtle:

(1) qp^2 is not negative. This means the value could be zero or positive. Whenever you square either a positive or a negative number squared the result is positive number. But we also need to check for zero, and zero squared is zero. So p^2 could be + or 0. And the same goes for q. In order to get a positive number, if p^2 is positive, then q must also be positive. But because we can't rule out a value of qp^2 = 0, q could = 0 or +.

INSUFFICIENT

(2) q^2 is positive. Following the logic of exponents above, a negative or a positive squared creates a positive, so q could either be negative or positive.

INSUFFICIENT

Together, we know qp^2 is not negative and we know that q^2 is positive. Through statement 2 we know that q is not zero, and therefore q must be a positive number in order to make statement 1 true.

Thus, the answer is C.
this is what I worked out before reading shovan's answer.

M confused now.

Whats the oa nightreader ?
Cheers !!

Quant 47-Striving for 50
Verbal 34-Striving for 40

My gmat journey :
https://www.beatthegmat.com/710-bblast-s ... 90735.html
My take on the GMAT RC :
https://www.beatthegmat.com/ways-to-bbla ... 90808.html
How to prepare before your MBA:
https://www.youtube.com/watch?v=upz46D7 ... TWBZF14TKW_
Join the discussion

by clock60 » Mon Jan 10, 2011 9:46 am
hi aleph777
i think you miss that p^2 can be equals to 0, as we have no restrictions on p, if p^2=0, then
(-q)*0>=0 here q-ve
(q)*0>=0 here q+ve
Join the discussion

by aleph777 » Mon Jan 10, 2011 9:48 am
clock60 wrote:hi aleph777
i think you miss that p^2 can be equals to 0, as we have no restrictions on p, if p^2=0, then
(-q)*0>=0 here q-ve
(q)*0>=0 here q+ve
Great point, Clock60!
Join the discussion

by chendawg » Mon Feb 14, 2011 12:53 pm
I would have to go with E as well here.
Join the discussion

by Night reader » Mon Feb 14, 2011 1:02 pm
OA is E
Join the discussion

by thebigkats » Fri Feb 18, 2011 12:56 pm
(1)
q*p^2 = not-negative = 0 or +ve
==> if (q*p^2 = positive) then - q = +ve
==> if (q*p^2 = 0) then q = 0 or p^2 = 0
==> if p^2 = 0 then q = +ve or -ve or 0
INSUFF

(2)
q^2 = +ve
==> q = +ve or -ve (not zero)
INSUFF

(1&2):
q = +ve or -ve

Hence - (E)
Join the discussion

by thp510 » Mon Feb 28, 2011 2:09 am
Night reader wrote:Is q positive?

(1) qp^2 is not negative
(2) q^2 is positive


If (1) was re-worded to say: q(p^2) is not positive than the OA would be A correct? I initially thought it was q(p^2) and not (qp)^2
Join the discussion

by Anurag@Gurome » Mon Feb 28, 2011 8:11 pm
thp510 wrote:
Night reader wrote:Is q positive?

(1) qp^2 is not negative
(2) q^2 is positive


If (1) was re-worded to say: q(p^2) is not positive than the OA would be A correct? I initially thought it was q(p^2) and not (qp)^2

So the question will be :
Is q positive?
(1) q(p^2) is not positive
(2) q^2 is positive



Solution:
Let us first consider (1) alone.
This means q(p^2) <= 0
Let q = 3 and p = 0.
Here, q(p^2) = 0 and q is positive.
Next, let q = -3 and p = 0.
Again, q(p^2) = 0 and q is negative.
So, we cannot say from (1) that q is always positive or not.
Hence, (1) alone is not sufficient to answer the question.
Next consider (2) alone.
It only means that q is not zero.
But we cannot say whether q is positive or not.
Or (2) alone is not sufficient.
Next, combine both the statements together and check.
Even on combining, we get that q can be positive or negative.
This can be verified using (p,q) as (0,-3) and (0, 3) respectively.
Or both statements together are not sufficient to answer the question.

The correct answer is (E).
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Join the discussion

by thp510 » Tue Mar 01, 2011 12:39 am
Anurag@Gurome wrote:
thp510 wrote:
Night reader wrote:Is q positive?

(1) qp^2 is not negative
(2) q^2 is positive


If (1) was re-worded to say: q(p^2) is not positive than the OA would be A correct? I initially thought it was q(p^2) and not (qp)^2

So the question will be :
Is q positive?
(1) q(p^2) is not positive
(2) q^2 is positive



Solution:
Let us first consider (1) alone.
This means q(p^2) <= 0
Let q = 3 and p = 0.
Here, q(p^2) = 0 and q is positive.
Next, let q = -3 and p = 0.
Again, q(p^2) = 0 and q is negative.
So, we cannot say from (1) that q is always positive or not.
Hence, (1) alone is not sufficient to answer the question.
Next consider (2) alone.
It only means that q is not zero.
But we cannot say whether q is positive or not.
Or (2) alone is not sufficient.
Next, combine both the statements together and check.
Even on combining, we get that q can be positive or negative.
This can be verified using (p,q) as (0,-3) and (0, 3) respectively.
Or both statements together are not sufficient to answer the question.

The correct answer is (E).
Thanks Anurag. Yes, I forgot about 0 (which is like a "third" sign).
Join the discussion

by LalaB » Mon Oct 24, 2011 10:12 pm
I have chosen C too ) and actually could not understand ur reasoning of rejecting C option. ((

we are not asked whether qp is positive. we are asked whether Q is positive.

stmt 1 qp^2 is not negative- insuff, since "not negative" means (+) or 0.

stmt 2 q^2 is positive -insuff, since q can be (+) or (-)

both stmts- because of stmt 1, q cant be (-), so q must be (+) . and yes p could still be 0, but it doesnt change the situation of q alone. q can not be 0, since from stmt 2 we know that q is either positive, or negative. 0 is neither positive, nor negative.

please explain me what is wrong in my way of thinking.

thnx
Join the discussion