This is really hard for me to explain.

Say I have 2 numbers, 20 and 800

20 will decreased by a constant and added to itself

(Say the constant is .2, it will be 20 + 19.8, + 19.6 etc...)

Now, How do I find the constant so that with all the numbers added will make 800?

( )

And how would I write the equation to go with that that's not as long as the one stated above this text.

If I'm not so clear on the question, I'll try to describe it better.

(Also, A quick method on adding consecutive reals together would be nice)