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Directions

This data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements, plus your knowledge of mathematics and everyday facts (such as the number of days in a leap year or the meaning of the word counterclockwise), you must indicate whether -

1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
3. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
4. EACH statement ALONE is sufficient to answer the question asked.
5. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Numbers
All numbers used are real numbers.

Figures
A figure accompanying a data sufficiency question will conform to the information given in the question but will not necessarily conform to the additional information given in statements (1) and (2).

Lines shown as straight can be assumed to be straight and lines that appear jagged can also be assumed to be straight.

You may assume that the positions of points, angles, regions, etc. exist in the order shown and that angle measures are greater than zero.

All figures lie in a plane unless otherwise indicated.

Note
In data sufficiency problems that ask for the value of a quantity, the data given in the statement are sufficient only when it is possible to determine exactly one numerical value for the quantity.

Is ab positive?
1. (a+b)² < (a-b)²
2. a = b

The correct choice is (A). The correct answer is statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

The given question is an "Is" question. So, the answer has to be a definite YES or a definite NO. It cannot be a MAYBE.

Let us evaluate statement 1.

Expanding both sides of the inequality, we get a² + b² + 2ab < a² + b² - 2ab

Simplifying we get, 4ab < 0 or ab < 0.

So, we can convincingly answer that ab is not positive. So, statement 1 is sufficient to answer the question.

The correct answer is either A or D.

Now let us evaluate the statement 2.

This is actually the statement that could trick you.

a = b.

So, either both a and b or positive or both a and b are negative. In either case ab is positive.
We will certainly be "tempted" to decide that statement 2 is also sufficient.

The catch is that, both a and b could be 0. In that case ab = 0, which is not positive.

As we are not able to conclude if ab is positive or not with statement 2, it is not sufficient.

Hence, answer is choice (A ).