单选题 Which of the following procedures is always equivalent to adding 5 given numbers and then dividing the sum by 5?
Ⅰ Multiplying the 5 numbers and then finding the 5 th root of the product.
Ⅱ Adding the 5 numbers, doubling the sum, and then moving the decimal point one place to the left.
Ⅲ Ordering the 5 numbers numerically and then selecting the middle number.
(A) None
(B) Ⅰonly
(C) Ⅱonly
(D) Ⅲonly
(E) ⅠandⅢ

【正确答案】 C

【答案解析】[解析] 此题也就是问哪一做法等同于把五个数求算术平均值。Ⅰ很明显是对五个数求几何平均值的程序，而几何平均值与算术平均值在大多数的情况下是不相等的，所以Ⅰ不正确；而Ⅲ是求五个数的中数，中数与算术平均数同样在大多数情况下是不同的，所以Ⅲ也不正确；Ⅱ相当于把五个数的和乘以2再除以10，所以相当于把五个数求算术平均值。