Reducing scale

I am sizing some landscaping, and I measured everything on a 20 to 1 scale. I realized when I was done that it was at 30 to 1. How can I convert what I already have to 30 to 1. For example, if the grass area is 22,871.6' at 20 to 1, how do you figure it out to be 30 to 1?

Final Answer:

k =  0.6667

Step-by-step explanation:

$$\begin{gathered} k=\frac{20}{30}=\frac{2}{3}\doteq 0.6667 \\ A=228716 \\ B=k\cdot A=\frac{2}{3}\cdot 228716=\frac{2\cdot 228716}{3}=\frac{457432}{3}\doteq 152477.3333 \\ k=\frac{2}{3}=0.6667 \end{gathered}$$

Try another example