单选题 X,81,73, 71,98, 73,64What is the value of X in the above list of 7 numbers ?(1) The average (arithmetic mean) of these 7 numbers is 80. (2) The range of these 7 numbers is 36.

A、 Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B、 Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C、 BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D、 EACH statement ALONE is sufficient.
E、 Statements (1) and (2) TOGETHER are NOT sufficient.

【正确答案】 A

【答案解析】(1) Since the average of the seven numbers is 80, it follows that the sum of theseven numbers is 7(80) = 560. Therefore, X+ 81 + 73 + 71 + 98 + 73 + 64 = 560, which can be solved for a unique value of X; SUFFICIENT.(2) The range of the numbers when X is not included is 98 - 64 = 34. Therefore, if X= 98 + 2 = 100, then the range of the seven numbers is 100 - 64 = 36, and if X= 64 - 2 = 62, then the range of the seven numbers is 98 - 62 = 36. Therefore, more than one value of X satisfies the given information and statement 2; NOT sufficient.The correct answer is A; statement 1 alone is sufficient.