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smc

counting and probability senior

Problem

How many sets of two or more consecutive positive integers have a sum of ?
(A)
(B)
(C)
(D)
Solution
Notice that if the consecutive positive integers have a sum of , then their average (which could be a fraction) must be a divisor of . If the number of integers in the list is odd, then the average must be either or , and is clearly not possible. The other two possibilities both work: If the number of integers in the list is even, then the average will have a . The only possibility is , from which we get: * Thus, the correct answer is Question: (RealityWrites) Is it possible that the answer is , because should technically count, right? Answer: (IMGROOT2) It isn't possible because the question asks for positive integers, and this means that negative integers or zero aren't allowed. Note to readers: make sure to always read the problem VERY carefully before attempting; it could mean the difference of making the cutoff.
Final answer
C