Bunuel
What is the average of the consecutive integers m through n, inclusive?
(1) The average of m and n is 23.5
(2) The average of the integers between m and n not including either is 23.5
We need to find the average of consecutive integers whose lowest item is m and whose highest item is n, or vice versa.
We should see that consecutive integers are consecutive terms in an arithmetic sequence. For any arithmetic sequence, the average of terms can be determined with the following formula:
Average = (Lowest value + Highest value)/2
So, the question is:
(m + n)/2 = ?
Statement One Alone:=> The average of m and n is 23.5
(m + n)/2 = 23.5
Statement one is sufficient. Eliminate answer choices B, C, and E.
Statement Two Alone:=> The average of the integers between m and n not including either is 23.5
We see that the integers between m and n are consecutive terms in an arithmetic sequence.
So, if m is less than n, the average of terms for this shorter sequence is:
[(m + 1) + (n - 1)]/2 = 23.5
(m + n)/2 = 23.5
Statement two is sufficient.
Answer: D