Yes/No questions

Question

Hi, I'd like an example of a DS question where it answers 'no' only. 
It's agreed that if a DS question answers 'no' it's also sufficient but I've encountered one yet.
Could post some, please and thanks

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deepverma · Answer

Sure, here you go https://gmatclub.com/forum/if-xy-0-is-x ... 12566.html

Kinshook · Answer

Hi  Waridi

A very simple example, though not of GMAT level: -

Is x=0?
1. x=1
2. x=3
The answer is NO in both the cases.

OA D

IanStewart · Answer

You cannot see a GMAT question like this, because the two Statements are contradictory (they cannot both be true).

I think this is a simple example of the type of question that people often answer incorrectly when they're just beginning to learn about how DS works:

Is a = 5?
1. a > 3
2. a > 7

Using Statement 1, it is possible that a is 5, but possible that a is not 5. So Statement 1 is not sufficient.

Using Statement 2 alone, we can be absolutely certain that a is  not  equal to 5. So we can be certain the answer to the question is "no", and Statement 2 is sufficient alone.

Most of the time, on the real GMAT, when a Statement provides enough information to answer a yes/no DS question, the answer turns out to be 'yes'. So if you study from the OG, say, you won't find many questions similar to the one above, where we can definitively prove the answer to the question is "no". You do occasionally see questions with definite "no" answers on the real test though, so you should be aware of how to answer them. That said, some prep companies make far too big a deal about this issue (in some prep company problem sets, you can get a certain "no" answer more often than a certain "yes" one, which is not at all similar to what you'll see on the actual test).

Yes/No questions

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