Reducing scale

I am sizing some landscaping and measured everything at a scale of 20:1. I then realised the scale should have been 30:1. How can I convert my existing measurements to 30:1? For example, if a grass area measures 22,871.6 at 20:1, how do you calculate the correct measurement at 30:1?

Final Answer:

k =  0.6667

Step-by-step explanation:

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

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