SOLUTION: the formalua you use to find the sum of 1-1000 1+2=3+3=6+4=10+5=15 ..... Thank you!

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Question 497220: the formalua you use to find the sum of 1-1000
1+2=3+3=6+4=10+5=15 ..... Thank you!
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Here's the formula:
%28a%5B1%5D%2Ba%5Bn%5D%29%28n%2F2%29 Where: a%5B1%5D is the first number (That's number 1), a%5Bn%5D is the nth number (that's 1000), and n is the number of numbers (that's 1000).
So...
%281%2B1000%29%281000%2F2%29+=+%281001%29%28500%29=500,500