Official Guide Explanation:
Data Sufficiency #84

Background

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Solution and Metadata

Question: 84
Page: 280
Difficulty: 5 (Moderate)
Category 1: Algebra > Linear Equations-Two Unk >
Category 2: Arithmetic > Descriptive Statistics > Average

Explanation: The average of j and k is ((j + k)/2), so all we need is the sum of j and k. Statement (1) is sufficient: to write this statement as an equation looks like this:

((j + 2 + k + 4)/2) = 11

j + 2 + k + 4 = 22

j + k + 6 = 22

j + k = 16

Given the sum of j and k, you can find the average. Statement (2) is also sufficient:

((j + k + 14)/3) = 10

j + k + 14 = 30

j + k = 16

Again, we're able to find the sum of j and k. Note that the individual values of j and k are not important; we only need the sum to answer the question. Both statements are sufficient, so choice (D) is correct.

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