Data Sufficiency

pepeprepa wrote:Is it possible to get the answer in the question in DS?
I was also wondering, is it possible to find an answer with 1) only and another solution with 2) only ? Or there is only one solution to the question?

Good questions- on the real GMAT, DS questions will always follow these rules:

-it will never be possible to answer the question without using additional information;

-the two statements will never contradict each other.

Some questions designed by test prep companies do not, however, obey these rules- which usually doesn't inspire me with much confidence in the value of these questions.

So, you'll *never* see GMAT questions like the following:

If x is an integer, and x > 10, is x odd?
1) x is prime
2) x + 2 is even

The two statements contradict each other (if x > 10, the first statement ensures x is odd, while the second ensures that x is even)- they can't both be true. Illegal on the GMAT.

If x is an integer, and 2 < x < 4, what is the value of x?
1) x^2 = 9
2) |x-3| = 0

You know from the stem that x = 3; you don't need any of the statements. Again, illegal on the GMAT.

This means that on real GMAT DS questions, if you think you can answer the question without additional information, you've misunderstood the question. If the two statements appear to give contradictory information, you've misunderstood one of the statements. You can't apply these tests on questions from some test prep companies, however- not all questions are well-designed.

Finally, I'm just as mystified as Stuart about the question in the original post - why do we need the statements at all? My guess is that the question should read: "A shop sold 3/4 of the sweaters in its inventory...", which is then an appropriate DS question.