第四十一题 【考古】:GWD数学第19套32题。关于平均数和中位数 A certain list consists of 3 different numbers. Does the median of the 3 numbers equal the average (arithmetic mean) of the 3 numbers? (1)The range of the 3 numbers is equal to twice the difference between the greatest number and the median. (2) The sum of the 3 numbers is equal to 3 times one of the numbers. 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. Answer: D 条件1对,设最小数是a,最大数是c,中位数是b,若平均数=中位数则:(a+b+c)/3=b,化简得a+c=2b。 根据条件1的表述,刚好就是a+c=2b,故成立 条件2对,因为总共就这么三个数,平均值不可能等于最大数或者最小数的2倍,必定是中位数的2倍,故成立