Treadmill 70904

The runner circled the track three times. If he went around it once more, he would run one kilometer. What is the radius of the treadmill?

Correct answer:

r =  39.79 m

Step-by-step explanation:

$$\begin{gathered} (3+1)o=1km \\ 4o=1000m \\ 4\cdot 2\pi \cdot r=1000 \\ r=\frac{1000}{4\cdot 2\pi }=\frac{1000}{4\cdot 2\cdot 3.1416}=39.79\text{m} \end{gathered}$$

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