Larger the input; the smaller the output

I wasn't really sure where to post this thread so I thought "Other" was appropriate. Anyways, I am building a spreadsheet and have run into a math problem that I have failed to comprehensively work through.

Here it is:

In the spreadsheet I have some resources adding up to a total. We will call this X. It will be the input.

Secondly, The larger X is the less time it will take.This is the output, we will call this Y.

So resources =X

Time =Y

X(some math goes here)=Y

Here is some base numbers to work with. If X = 10 thru 12; then Y = 1 sec.

I know there is most likely some simple high school math involved in here but, I'm a person that need not so much math in life so ya.

I appreciate any help on this problem if anyone is up to it.

Thank-You