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smc

algebra senior

Problem

Which one of the following integers can be expressed as the sum of consecutive positive integers?
(A)
(B)
(C)
(D)
Solution
The sum of the first integers is . If you add an integer to each of the numbers, you get , which is the sum of the numbers from to . You're only adding multiples of , so the last two digits will remain unchanged. Thus, the only possible answer is , because the last two digits are . As an aside, if , then , and the numbers added are the integers from to .
Final answer
A