NUMBER SEQUENCE HELP!! 1

[cadshite]

Can anyone help me find a formula to find the nth term of 1+2+3+4+5+6+7+8+....n = ???
i.e if n=8 then the answer is 36, so if for e.g i wanted to find the answer to n=1000 i can use a formula.
Thanks, not too sure if this is the right forum but there aren't a great deal of maths ones!

 

[davidbeach]

(n+1)/2

 

[cadshite]

Thanks, dont suppose you could tell me how to work that out too?? I managed to guess it was a quadratic formula but couldnt work out a b or c values.

 

[IRstuff]

You could just try and use Google:

http://www.cs.brown.edu/~rbb/summermath/GS2001.wk2.html

TTFN

 

[cadshite]

Thanks old chap - i did try using google but came up with other stuff. Try some of these (if your bored, very bored of course!)

http://mathworld.wolfram.com/topics/Puzzles.html

 

[bkal]

Not exactly a 'proper' explanation, but you can look at the problem like this:
- adding up the first and the last number in a series gives (n+1),
- there is n/2 pairs like that,
- so to get a total sum, you just multiply (n+1)*n/2