GMAT OFFICIAL GUIDE DS

Solution:

We are given the following expression: S = (2/n)/(1/x + 2/(3x)), and we must determine a value for S. Before moving to the statements, we want to simplify the given expression. To do this, we use the common denominator 3x and then combine the fractions 1/x and 2/(3x).

3/(3x) + 2/(3x) = 5/(3x)

Let’s substitute this into our original expression.

S = (2/n)/(5/(3x))

We can now perform the division of the two fractions by inverting and multiplying:
S = 2/n * 3x/5

S = 6x/(5n)

Statement One Alone:

x = 2n

Since x = 2n, we can substitute 2n for x in the equation S = 6x/(5n).

S = 6(2n)/(5n)

S = 12n/(5n)

S = 12/5

Since we have determined a value for S, statement one alone is sufficient to answer the question. We can eliminate answer choices B, C, and E.

Statement Two Alone:

n = ½

Since n = ½ we can substitute ½ for n in the equation S = 6x/(5n).

S = 6x/2.5

Because we do not have a value for x, we cannot determine the value of S. Statement two alone is not sufficient to answer the question.

Answer: A

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