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# If ab=1, what is the value of (axb) (ayb) ?

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Intern
Joined: 19 Sep 2010
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If ab=1, what is the value of (axb) (ayb) ? [#permalink]  31 Dec 2010, 19:58
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Difficulty:

45% (medium)

Question Stats:

60% (01:32) correct 40% (00:25) wrong based on 30 sessions
If ab=1, what is the value of (axb) (ayb) ?

(1) ax=by=2
(2) 2xy=4

Source is manhattan review math sheet.
[Reveal] Spoiler: OA
Manager
Joined: 18 Oct 2010
Posts: 93
Followers: 2

Kudos [?]: 7 [0], given: 0

Re: don't know how to crack [#permalink]  01 Jan 2011, 01:35
naaga wrote:
If ab=1, what is the value of (axb) (ayb) ?
1. ax=by=2
2. 2xy=4

source is manhattan review math sheet.

$$axb)(ayb)=(ab)(xa)(yb)=1*2*2=4 2/2xy=4 so xy=1 so (axb)(ayb)=(ab)(ab)(xy) there you go D Math Expert Joined: 02 Sep 2009 Posts: 27542 Followers: 4329 Kudos [?]: 42659 [1] , given: 6052 Re: don't know how to crack [#permalink] 01 Jan 2011, 02:42 1 This post received KUDOS Expert's post naaga wrote: If ab=1, what is the value of (axb) (ayb) ? 1. ax=by=2 2. 2xy=4 source is manhattan review math sheet. any one please explain the answer, thanks in advance.. Given: \(ab=1$$. Question: $$(axb)*(ayb)=?$$

(1) ax=by=2, so $$ax=2$$ and $$by=2$$ --> $$(axb)*(ayb)=(ax)*(by)*(ab)=2*2*1=4$$. Sufficient.
(2) 2xy=4, so $$xy=2$$ --> $$(axb)*(ayb)=(ab)*(ab)*(xy)=1*1*2=2$$. Sufficient.

Now, technically answer should be D, as EACH statement ALONE is sufficient to answer the question.

But even though formal answer to the question is D (EACH statement ALONE is sufficient), this is not a realistic GMAT question, as: on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

So we can not have answer 4 from statement (1) and answer 2 from statement (2), as in this case statements would contradict each other.

I guess statement (2) should read xy=4 instead of 2xy=4, in this case answer will be D and the statements won't contradict each other.

Hope it's clear.
_________________
Re: don't know how to crack   [#permalink] 01 Jan 2011, 02:42
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