klamation wrote:Perhaps I'm nitpicking, but I think this question is a little unclear. Just because 100 of the red sweaters are NOT wool doesn't mean that the remaining 50 ARE wool. They could be cotton or polyester, or whatever. If it were the other way around it and the question was "how many of the red sweaters are not made from wool" and statement 2 was "100 of the red sweaters are made from wool", we can infer statement 2 to be sufficient.
There is nothing ambiguous or unclear about statement 2.
Something is either X or not X.
A number is either an integer or not an integer.
A person is either male or not male.
A sweater is either made of pure wool or not made of pure wool.
In the DS question above, every red sweater is either made of pure wool or not made of pure wool.
Thus, if 100 of the 150 red sweaters are not made of pure wool, then the remaining 50 red sweaters are made of pure wool.
The 100 not-pure-wool sweaters include every red sweater made of a fabric aside from pure wool (cotton, poly, rayon, etc.).
This sort of logic is common in DS questions:
If 30 of the 100 people in the room are not scientists, then the remaining 70 people are scientists.
If 40 of the 50 states are not covered in snow, then the remaining 10 states are covered in snow.
If 100 of the 150 red sweaters are not made of pure wool, then the remaining 50 red sweaters are made of pure wool.
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