Aus Online Mathematik Brückenkurs 1

Because the wheel's circumference is

\displaystyle 2\pi \centerdot radius metres metres

the wheel turns \displaystyle \pi metres on each revolution, and in \displaystyle \text{1}0 metres the wheel therefore turns

\displaystyle \frac{10\ \text{metres}}{\pi \ \text{metres}}=\frac{10}{\pi }\approx 3.2 revolutions