Sum of Alternating Integers

What is the value of 1+\textrm{-}2+3+\textrm{-}4+\cdots+99+\textrm{-}100 (alternating signs for each term)?
Source: NCTM Mathematics Teacher 2006

SOLUTION
The sum consists of 50 additions of a positive and a negative integer each resulting in \textrm{-}1
1+\textrm{-}2=\textrm{-}1
3+\textrm{-}4=\textrm{-}1
\cdots
97+\textrm{-}98=\textrm{-}1
99+\textrm{-}100=\textrm{-}1
1+\textrm{-}2+3+\textrm{-}4+\cdots+99+\textrm{-}100=\textrm{-}50

Answer: \textrm{-}50

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About mvtrinh

Retired high school math teacher.
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