Data Sufficiency - Average age of group

XAT 2018 · Quantitative Ability & Data Interpretation · Medium · Data Sufficiency

These statements provide data that may help answer the respective questions. Read the questions and the statements and determine if the data provided by the statements is sufficient or insufficient, on their own or together, to answer the questions. Accordingly, choose the appropriate option given below the questions.

A group of six friends noticed that the sum of their ages is the square of a prime number. What is the average age of the group?

Statement I: All members are between 50 and 85 years of age. Statement II: The standard deviation of their ages is 4.6.

  1. A.

    Statement I alone is sufficient to answer.

  2. B.

    Statement II alone is sufficient to answer.

  3. C.

    Either of the statement is sufficient to answer.

  4. D.

    Both statements are required to answer.

Answer

A

Explanation

Sum of ages of 6 friends is the square of a prime number p2p^2. From Statement I, each member is between 50 and 85 years old. Sum of ages is between 6×50=3006 \times 50 = 300 and 6×85=5106 \times 85 = 510. The only square of a prime number in this range is 192=36119^2 = 361. Therefore, the sum of their ages must be 361, and the average age is 3616\frac{361}{6}. Thus, Statement I alone is sufficient. Statement II alone does not provide the sum or mean. Thus, option A is correct.

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