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DS Choice Confusion

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DS Choice Confusion

by vineetmittal04 » Thu Jun 05, 2014 7:52 am
Hi, I have a doubt regarding the choice selection in DS questions.

I want to know that if the question asks to find a value and I am getting a different value from each
of the statements, what will be the answer choice? Should I choose, "Each statement alone is sufficient" or "More information is required".

Similarly, if the question asks, for example, to tell whether a variable is greater than zero. Then the answer would be "Yes, it is greater than zero" or it can be a "No, it is not greater than zero" as well. Because in either case I can answer "Yes" or "No" using the statement. So, in case of a "No", can I select "The statement is sufficient to answer the question".

It will be really helpful if someone could clear this confusion for me.
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by Brent@GMATPrepNow » Thu Jun 05, 2014 9:17 am
I want to know that if the question asks to find a value and I am getting a different value from each
of the statements, what will be the answer choice? Should I choose, "Each statement alone is sufficient" or "More information is required".
The two statements in a DS question will NOT contradict each other.
Consider this example:
What is the value of x?
1) 2x = 6
2) x + 1 = 8
The above cannot be a true DS question, because the two statements contradict each other. Statement 1 tells us that x = 3, and statement 2 tells us that x = 7.

For more on this feature of DS questions, you can watch our free video titled "Useful Contradictions": https://www.gmatprepnow.com/module/gmat- ... cy?id=1104
Similarly, if the question asks, for example, to tell whether a variable is greater than zero. Then the answer would be "Yes, it is greater than zero" or it can be a "No, it is not greater than zero" as well. Because in either case I can answer "Yes" or "No" using the statement. So, in case of a "No", can I select "The statement is sufficient to answer the question".
If you can answer the target question with certainty, then it does not matter whether the answer to the target question is "yes" or "no"
Consider this example:
Is x positive?
1) 2x = -6
2) x² = 9
Statement 1 tells us that x = -3. So, we can answer the target question with certainty. The definitive answer here is "x is definitely NOT positive." So, statement 1 is SUFFICIENT.
Statement 2 tells us that EITHER x = -3 OR x = 3. So, we cannot be certain whether or not x is positive. So, statement 2 is NOT SUFFICIENT.
Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by vineetmittal04 » Thu Jun 05, 2014 9:58 am
Thank you Brent. It cleared my confusion.

Regards,
vineet
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by [email protected] » Thu Jun 05, 2014 3:34 pm
Hi vineetmittal04,

DS questions are about "consistently" vs. "inconsistency."

After working through the first Fact/Statement, if you find that the answer to the question stays the SAME, then it does not matter what the answer is because it's consistent (and thus SUFFICIENT). If the answer CHANGES, then the first Fact/Statement is inconsistent (and thus INSUFFICIENT).

This applies to all DS questions, whether they are "value" questions or "yes/no" questions.

Make sure to be thorough when you work on DS questions. You'll find it pretty easy to find AN answer to a given prompt, but you have to do enough work to be sure if its the only answer or if there are other (different) answers.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
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