MGMAT: Question bank: Is Is pq = 1?

[guest]

Is pq = 1?

(1) pqp = p

(2) qpq = q

Solving for the statements:

For 1 : p = 0 or pq=1

For 2: q=0 or pq = 1

Since pq =1 for both statement, isn't it sufficient? So p or q doesn't = 0, since pq=1. I chose C but the answer is E. Help please
. thx

[StaceyKoprince]

Remember that pq = 1 is the question. We don't know whether it's actually true; it might be false. Only the two statements are given as true.

So, for statement 1, p could be 0, and then pqp = p would be 0 = 0 (regardless of what q is), and the answer to the question "is pq = 1?" is no.
Or, p could be 1 and q could be 1. Then pqp = p would be 1=1, and the answer to the question "is pq = 1?" is yes.

[yousuf_azim]

What is ans?

BR

[StaceyKoprince]

Please make sure to read the complete post before replying. The original poster indicated that the answer is E.

[aps_asks]

Hi Stacey ,

I have a doubt with regard to this question.

When -- Both Statement 1) and Statement 2) are indicating that pq =1 , then why the answer to this question is E) and not C).

Please let me know your comments.

[tim]

NEITHER statement says pq=1. they both say that pq=1 is ONE possibility but that something else can be true. note that p=q=0 is consistent with both statements as well..

[GMATFrenzy700+]

I too have the same doubt

From Stmt 1 => P = 0 or pq-1 = 0 which implies pq=1
From Stmt 2 => q= 0 or pq-1 = 0 which again implies pq = 1

From the 2 stmts together we know that pq=1 is the common comdition, therefore the answer is C.

COuld you please provide an alternate explanation so that we know why the correct answer is E

[NandKishore.Sagi]

I too have the same doubt

From Stmt 1 => P = 0 or pq-1 = 0 which implies pq=1
From Stmt 2 => q= 0 or pq-1 = 0 which again implies pq = 1

From the 2 stmts together we know that pq=1 is the common comdition, therefore the answer is C.

COuld you please provide an alternate explanation so that we know why the correct answer is E

GMATFrenzy:

This is my understanding. As per question stem we need to figure out what is the product of numbers p & q. We need to realize that we are dealing with two variables and not a single variable (p*q). We have to ensure that for all possible values of p and q the statements should hold true.

As you have analyzed the possible solutions for statement 1 are

p= 0 or pq = 1

Possible solutions for statement 2 are
q = 0 or pq =1

So at this stage both answer options A, B & D are out. So we are left with C & E. To figure out we need to answer a simple question can we ensure pq = 1 for all different values of P & Q ? The answer is NO because if P= 0 and Q = 0 then both statement 1 and 2 are satisfied but the product pq is not equal to 1.

Hence you cannot definitely say that pq =1

On a side note once I read this question my automatic answer choice was also C :-). Once I started analyzing the question stem more thoroughly I figured out that the answer choice is E and not C. One thing is clear for me got to stay extra alert in situations like these as I think many of us would fall into the pitfall of C. Thanks a lot to the original poster for this quesation.

[aps_asks]

Thanks all !

[tim]

let us know if you have any further questions on this one..