Is x = 0 ?
(1) xy = x
(2) x + y = y
answer is B
Why answer cannot be D. Statement (1) gives x = 0 or y = 1. It is giving x = 0. Why should we concerned about y = 1 when we are already getting x = 0 as it is being already asked ?
Thanks & Regards
Vinni
Is x = 0 ?
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Target question: Is x = 0 ?vinni.k wrote:Is x = 0 ?
(1) xy = x
(2) x + y = y
Statement 1: xy = x
There are several pairs of values for x and y that meet this condition. Here are two:
Case a: x = 0 and y = 2, in which case x = 0
Case b: x = 3 and y = 1, in which case x = 3
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: x + y = y
Subtract y from both sides to get x = 0
In other words, x must equal 0
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer = B
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Brent
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Hey vinni,
(10)*(1) = 10
(9)*(1) = 9
(8)*(1) = 8
and of course (0)*(1)= 0
Hence, you cannot say with absolute certainty that x = 0. Statement (1) is INSUFFICIENT.
Statement (2) just gives you what is asked in the prompt and is thus SUFFICIENT.
brgds,
Tobi
You seem to rule out the possibility that x can be something different than 0. But look closely at statement (1). As you say, y = 1. But then, numerous valous for X satisfy the equation xy = x. Here are some:Why should we concerned about y = 1 when we are already getting x = 0 as it is being already asked ?
(10)*(1) = 10
(9)*(1) = 9
(8)*(1) = 8
and of course (0)*(1)= 0
Hence, you cannot say with absolute certainty that x = 0. Statement (1) is INSUFFICIENT.
Statement (2) just gives you what is asked in the prompt and is thus SUFFICIENT.
brgds,
Tobi
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Good question, Vinni.vinni.k wrote: Why answer cannot be D. Statement (1) gives x = 0 or y = 1. It is giving x = 0. Why should we concerned about y = 1 when we are already getting x = 0 as it is being already asked ?
The problem is that you've reduced the strength of the question.
Yes, for statement 1, x could equal 0, but the target question doesn't ask, "Could x = 0?" The target question asks, "Does x = 0?"
In other words, "Must it be the case that x = 0?"
With all data sufficiency questions, a statement is sufficient if we are able to answer the target question with certainty.
In statement 1, we cannot answer the target question ("Does x = 0?") with absolute certainty, so it's not sufficient.
If you're interested, we have a free set of videos that cover everything you need to know about data sufficiency questions: https://www.gmatprepnow.com/module/gmat-data-sufficiency
Cheers,
Brent
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Thanks Brent. Actually i solved this question algebraically and didn't use different examples to verify the statement. This is where i make silly mistakes, and my questions get wrong and then i ask myself why my scores are not increasing.Brent@GMATPrepNow wrote: Statement 1: xy = x
There are several pairs of values for x and y that meet this condition. Here are two:
Case a: x = 0 and y = 2, in which case x = 0
Case b: x = 3 and y = 1, in which case x = 3
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Regards
Vinni