Bunuel wrote:

Is the average (arithmetic mean) of a and b less than 40?

(1) The average (arithmetic mean) of 3a and 3b is 117.

(2) b = 5a

We need to determine whether (a + b)/2 < 40, i.e., whether a + b < 80.

Statement One Alone:

The average (arithmetic mean) of 3a and 3b is 117.

Thus:

(3a + 3b)/2 = 117

3a + 3b = 234

a + b = 78

Statement one alone is sufficient to answer the question.

Statement Two Alone:

b = 5a

Since we do not know the values of a or b, we cannot determine whether a + b is less than 80.

Answer: A

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Jeffery Miller

Head of GMAT Instruction

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