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conty911
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Let denote a mathematical operation. Is it true that x y 25 Apr 2012, 22:35
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D
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85% (hard)

Question Stats:

28% (01:18) correct 72% (01:23) wrong based on 102 sessions

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Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?

(1)x ∇ y =1/x+1/y
(2) x ∇ y = x − y

There is little confusion regarding the statement 1.If values of x or y are plugged with '0', equation will become "not defined".Is that valid?
Source: Nova

This Question is Locked Due to Poor Quality
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D
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Bunuel
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Let denote a mathematical operation. Is it true that x y 25 Apr 2012, 23:52
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conty911
Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?
(1)x ∇ y =1/x+1/y
(2) x ∇ y = x − y

There is little confusion regarding the statement 1.If values of x or y are plugged with '0', equation will become "not defined".Is that valid?
Source: Nova
Show more

Yes, it would have been better if they've mentioned that \(xy\neq{0}\). But that's not the main problem with this question.

Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?

Theoretically if we know how function ∇ is defined we can answer the question even without going through any math. Since both statements define function ∇ then each statement is sufficient on its own and the answer must be D. But two statements below contradict each other, which is not possible. On the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

(1) x ∇ y = 1/x+1/y. So, y ∇ x = 1/y+1/x --> 1/x+1/y = 1/y+1/x for all x and y (assuming \(xy\neq{0}\)), so the answer to the question is YES. Sufficient.

(2) x ∇ y = x-y. So, y ∇ x = y-x --> x-y does not equal to y-x for ALL x and y, (consider x=2 and y=1), so the answer to the question is NO. Sufficient.

As you can see the statements clearly contradict each other: one gives an YES answer and another a NO answer.

Not a good question.
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Let denote a mathematical operation. Is it true that x y 30 Oct 2013, 07:24
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Bunuel
conty911
Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?
(1)x ∇ y =1/x+1/y
(2) x ∇ y = x − y

There is little confusion regarding the statement 1.If values of x or y are plugged with '0', equation will become "not defined".Is that valid?
Source: Nova

Yes, it would have been better if they've mentioned that \(xy\neq{0}\). But that's not the main problem with this question.

Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?

Theoretically if we know how function ∇ is defined we can answer the question even without going through any math. Since both statements define function ∇ then each statement is sufficient on its own and the answer must be D. But two statements below contradict each other, which is not possible. On the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

(1) x ∇ y = 1/x+1/y. So, y ∇ x = 1/y+1/x --> 1/x+1/y = 1/y+1/x for all x and y (assuming \(xy\neq{0}\)), so the answer to the question is YES. Sufficient.

(2) x ∇ y = x-y. So, y ∇ x = y-x --> x-y does not equal to y-x for ALL x and y, (consider x=2 and y=1), so the answer to the question is NO. Sufficient.

As you can see the statements clearly contradict each other: one gives an YES answer and another a NO answer.

Not a good question.
Show more

If the answer is A, could you please correct the OP ? Because it kinda records in workbook I believe, hence affecting practice.
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Let denote a mathematical operation. Is it true that x y 30 Oct 2013, 07:59
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kvazar
Bunuel
conty911
Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?
(1)x ∇ y =1/x+1/y
(2) x ∇ y = x − y

There is little confusion regarding the statement 1.If values of x or y are plugged with '0', equation will become "not defined".Is that valid?
Source: Nova

Yes, it would have been better if they've mentioned that \(xy\neq{0}\). But that's not the main problem with this question.

Let ∇ denote a mathematical operation. Is it true that x ∇ y = y ∇ x for all x and y?

Theoretically if we know how function ∇ is defined we can answer the question even without going through any math. Since both statements define function ∇ then each statement is sufficient on its own and the answer must be D. But two statements below contradict each other, which is not possible. On the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other.

(1) x ∇ y = 1/x+1/y. So, y ∇ x = 1/y+1/x --> 1/x+1/y = 1/y+1/x for all x and y (assuming \(xy\neq{0}\)), so the answer to the question is YES. Sufficient.

(2) x ∇ y = x-y. So, y ∇ x = y-x --> x-y does not equal to y-x for ALL x and y, (consider x=2 and y=1), so the answer to the question is NO. Sufficient.

As you can see the statements clearly contradict each other: one gives an YES answer and another a NO answer.

Not a good question.

If the answer is A, could you please correct the OP ? Because it kinda records in workbook I believe, hence affecting practice.
Show more

The answer is not A. Technically it's D. But the question is flawed.

This Question is Locked Due to Poor Quality
Hi there,
The question you've reached has been archived due to not meeting our community quality standards. No more replies are possible here.
Looking for better-quality questions? Check out the 'Similar Questions' block below for a list of similar but high-quality questions.
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