Data Sufficiency

[GMAT math practice question]

A data set contains 5 values: 11, 13, 15, 19, and x. What is the value of x?

1) The median of the 5 values is 15
2) The range of the data set is 8

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Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

Since we have 1 variable (x) and 0 equations, D is most likely to be the answer. So, we should consider each of the conditions on their own first.

Note: if the question doesn't include the phrase, "in increasing order", then x could be any number. In particular, it could be greater than or less than 19.



Condition 1):
Since the median is 15, we only know that x ≥ 15.
Condition 1) is not sufficient.

Condition 2):
Since the range of the values is 8, we have 11 ≤ x ≤ 19.
Condition 2) is not sufficient.

Conditions 1) & 2):
Both conditions 1) & 2) together yield 15 ≤ x ≤ 19. But this does not tell us the exact value of x. We do not have a unique solution.
Thus, both conditions together are not sufficient.

Therefore, E is the answer.

Answer: E