Let the three numbers be
a, b, and c
Expression to compare:
(a+b+c)/3
I. Ordering the numbers from highest to lowest and selecting the middle number:
This is selecting the median of the three numbers.
The median is the middle value, but it is not always equal to the average, especially if the three numbers are not evenly spaced.
So statement I is
not always equivalent to the average.
II. Dividing each of the numbers by 3 and then adding the results:
a/3 + b/3 + c/3 = (a+b+c)/3
This matches the average formula exactly.
Therefore, statement II is
always equivalent.III. Multiplying each number by 6, adding the result, then dividing the sum by 9:
(6a+6b+6c)/9 = 2(a+b+c)/3
This is 2/3 times the sum, not the average (unless the sum happens to be zero or other special cases).
Therefore, statement III is
not equivalent to the average.
The correct answer is
B: II only.