If A1 contains of total quantity purchased then

=400*A1-70*0.5*(A1^2-A1)

will be the total amount paid
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Gary's Student
gsnu200701


"Tracker" wrote:

Hi. Im trying to set something up where I put a number(y) in a cell that
represents the quantity of x. (x is the product Im buying and y is the
amount). The thing is that after I buy one for say 400, the next time I buy
It will cost 330, and the number decreases by 70 every time i buy. Is there
an easy way to total up the cost of (y) amount of (x). Example:
need to buy 3 boxes: 1st box costs 400;2nd box costs 330;3rd box costs 260
total: 990
How do I automatically calculate the total by putting in the amount of
boxes needed in a cell in this situation.