Data Sufficiency

E as q can be 0 or a +ve integer

LalaB wrote: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

With both statements, you're right that q cannot be zero, but it CAN still be negative if and only if p is zero. For example, q=-1, p=0

Statement 1: qp^2=-1*0^2=0 which is non-negative

Statement 2: q^2=(-1)^2=1 which is positive.

so q=-1 and p=0 satisfy BOTH statements, so q CAN be negative (or positive, but you saw that already)

Hence, E

GmatMathPro wrote: With both statements, you're right that q cannot be zero, but it CAN still be negative if and only if p is zero. For example, q=-1, p=0

Statement 1: qp^2=-1*0^2=0 which is non-negative

Statement 2: q^2=(-1)^2=1 which is positive.

so q=-1 and p=0 satisfy BOTH statements, so q CAN be negative (or positive, but you saw that already)

Hence, E

oh I got what you mean! thank you for ur explanation! ) now everything is clear! thnx

IMO its an E only

Night reader wrote:Is q positive?

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

Since the first statement says it is positive, and the numbers are raised to an even exponent, we know that this hides the true sign of q. q could be negative or positive. Thus, it is insufficient

The second statement is the same as the first statement. q can be negative or positive. Thus, this one is also insufficient.

Together, the statements still say the same thing, no additional information is given by either, so they are both insufficient together.

The answer = E

Fell for C.

Realized my mistake though. When both statements are considered together, I assumed q=1. But missed the point that p=0, q=-1 still gives q(p)^2 as non-negative.

Nice one.

Typical gmat trap problem. When we rush through, we overlook these wordings.
Chose C

"Non Negative =>both 0 and +ve values".

C is the answer.

q is positive.
q > 0

Is q positive?

1. qp^2 is not negative.
2. q^2 is positive. NS

Doubt abt st. 1
Is it q*p^2 or (qp)^2?

1. Eye catching statement qp^2 is not negative - so it can be 0 or +ive
so q can -ive or ive.

2 for q^2 to be positive , q can -ive or ive. so 2 is not sufficient

Answer E

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Is q positive?

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

In the original condition there is 1 variable (q) but overall there are 2, (p,q) thus we need 2 equations to match the number of variables and equations. Since we have 1 each in 1) and 2), C is likely the answer.
Using both 1) & 2) together, q=-1, p=0 no, q=1, p=0 and the answer is yes therefore it is not sufficient. The answer is E (we need to consider 0 in non-negative case)




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LalaB wrote: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

Here you are not taking possibility of q = 0 so we can say that q is 0 or +ive