If I am riding my push mountain bike at 25 km/h, and my tyre radius is 30.5 cm.

How many revolutions per minute are my wheels travelling at?

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- Apr 8th 2013, 08:17 PM #1

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- Apr 8th 2013, 08:32 PM #2

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## Re: please help with this problem

$\displaystyle 25 \quad\text{km/h}= \frac{25000 \quad\text{m}}{60 \quad\text{mins}} = 416.\dot{6}\,\,\text{m/min} $

$\displaystyle 1$ revolution of the wheel covers $\displaystyle 2\pi r= 2\pi(0.305)=1.9163...\text{m}$ so $\displaystyle \416.\dot{6}\,\,\text{m}=\frac{416.\dot{6}}{1.9}\, \,\text{revs}$