Circular lawn

Around a circular lawn area is 2 m wide sidewalk. The outer edge of the sidewalk is curb whose width is 2 m. Curbstone and the inner side of the sidewalk together form a concentric circles. Calculate the area of the circular lawn and the result round to 10's m².

Correct result:

S =  1660 m²

Solution:

$$\begin{gathered} o=2\pi r \\ r=o\mathrm{/}(2\pi )=24.987 \\ S=\pi (r-2{)}^2=\pi (24.987-2{)}^2=1660{\text{m}}^2 \end{gathered}$$

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