[tex]0,5 \: hm=50 \: m \\
2 \: dam=20 \: m[/tex]
[tex]S= \frac{h \times l}{2} = \frac{20 \times 50}{2} = 10m \times 50m = 500 \: { m}^{2} [/tex]
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[tex]45 \: cm=0,45 \: m[/tex]
[tex]A = {l}^{2} = {0.45}^{2}m = 0.2025 \: {m}^{2} [/tex]