I need a function which is roughly (but not exactly) equivalent to $f(x)=\frac{1}{x}$ As $x$ varies from $0$ to $100$, $f(x)$ should vary from $20$ to $0$. Rough indications for values are as follows, to give an idea and know if I know things right:
\begin{array}{c|*5c} x& 4& 11& 20& 50& 80\\ \hline f(x) &18 & 15 & 12 & 5 & 2 \end{array} I am completely out of touch of maths. Please if someone can at least guide me in the right direction. I have filled several pages of notebook and now I'm getting confused.