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Weekly Problem 1 - 2008

Stage: 3 and 4 Challenge Level: Challenge Level:1

Given that the number 2008 is the correct answer to the calculation: $1-2+3-4+5-6+...+(n-2)-(n-1)+n$

What is $n$?

 

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.

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