Lake or pond

The landlord has a square lake. Trees grow around this lake. The lake wants to enlarge the pond twice and not cut down or flood any tree.

How will he do that?

Correct answer:

x =  0

Step-by-step explanation:

$$\begin{gathered} S_1=a^2 \\ {S}_2=\pi r^2 \\ 2\cdot S_1=S_2 \\ 2\cdot a^2=\pi r^2 \\ r=a\cdot \sqrt{2/\pi } \\ {h}_2=2\cdot h_1 \\ x=0 \end{gathered}$$

Try another example