Bunuel wrote:
What was the median monthly number of gallons of water used by the Jones family last year?
(1) The Jones family used 8,000 gallons of water during each of the first 6 months of last year.
(2) The Jones family used a total of 102,000 gallons of water last year.
n = 12 months, and we need to answer the question:
median = ?
Statement One Alone:=> The Jones family used 8,000 gallons of water during each of the first 6 months of last year.
Let’s imagine the monthly water usages, in thousands of gallons, in chronological order.
If {8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8}, then the ascending order of the monthly usages is the same, and the median = 8 thousand gallons.
Whereas, if {8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9}, then the ascending order of the monthly usages is the same, and the median = (8 + 9)/2 = 8.5 thousand gallons, which is the mean of the two middle values.
Statement one is not sufficient. Eliminate answer choices A and D.
Statement Two Alone:=> The Jones family used a total of 102,000 gallons of water last year.
If {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 102}, then the ascending order of the monthly usages is the same, and the median = 0 thousand gallons.
If {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 91}, then the ascending order of the monthly usages is the same, and the median = 1 thousand gallons.
Statement two is not sufficient. Eliminate answer choice B.
Statements One and Two Together:102 – 6 × 8 = 54 thousand gallons of water was used in the last 6 months.
If {8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 14}, then the ascending order of the monthly usages is the same, and the median = 8 thousand gallons.
Whereas, if {8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9}, then the ascending order of the monthly usages is the same, and the median = (8 + 9)/2 = 8.5 thousand gallons.
The two statements together are not sufficient.
Answer: E