One-third 2872

The cycling racetrack has the shape of a circle with an area of 2 ha. How long will a cyclist drive one-third of a kilometer in a perimeter?

Correct answer:

t =  1.504 min

Step-by-step explanation:

$$\begin{gathered} S=2\text{ha}\to {\text{m}}^2=2\cdot 10000{\text{m}}^2=20000{\text{m}}^2 \\ S=\pi r^2 \\ r=\sqrt{S/\pi }=\sqrt{20000/3.1416}\doteq 79.7885\text{m} \\ s=2\pi \cdot r=2\cdot 3.1416\cdot 79.7885\doteq 501.3257\text{m} \\ v=1000/3=\frac{1000}{3}\doteq 333.3333\text{km/min} \\ t=s/v=501.3257/333.3333=1.504\text{min} \end{gathered}$$

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