Explanation
The notation of this question is a little distracting,
because the vertical bars look like the symbols to indicate absolute value, but
in fact they indicate something else. No matter; we will keep the definition in
mind. We want to know whether
, according to the definition. And applying the
definition, that means that we want to know whether zero is the largest integer
less than or equal to n. If zero is
less than n, then n positive. And if zero is the largest one less than or equal to n, that means, for example, that 1 is
not less than or equal to n. So we
want to know whether n is greater
than 0 and less than 1. In other words, is
? Let's turn to the statements, separately first.
Statement (1) tells us that
, when we multiply through by 2. Reordering, it
means that
. We can analyze by cases. Case I:
. That's allowed by this statement. In that case,
the answer to our question is "yes," it's true that
. Case II:
. That's allowed by this statement, but in
Case II, the answer to our question is "no." Therefore, we have insufficient
information to answer the question definitively. Statement (1) is insufficient.
Statement (2) tells us that n is negative. What does that mean? We can consider a case. n could be -0.5, as we just discussed for
Statement (1). That case yields a "no." It could be a number such as -10, which
also yields a "no." We notice that in any case allowed by Statement (2), the
answer to the question will be "no." Therefore, we have sufficient information
to answer the question definitively. Statement (2) is sufficient.
The correct answer is (B).
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