Sea "P" la distancia que recorren las llantas en una revolución,
<img src="https://tex.z-dn.net/?f=P%3D2%5Cpi%20r%20%5C%5C%0AP%3D2%5Cpi%2A42%20%5C%5C%0AP%3D84%5Cpi%5Capprox%20263.89%5C%3Bcm" />
En un segundo, las llantas recorren :
<img src="https://tex.z-dn.net/?f=v%3D3P%3D3%2A84%5Cpi%0A%5C%5Cv%3D252%5Cpi%5Capprox%20791.68%20%5C%3Bcm%2Fs" />
Convirtiendo a km / h :
<img src="https://tex.z-dn.net/?f=v%3D252%5Cpi%20%20%5Cfrac%7Bcm%7D%7Bs%7D%20%5Ctimes%20%5Cfrac%7B1%5C%3Bkm%7D%7B100000%5C%3Bcm%7D%20%5Ctimes%20%5Cfrac%7B3600%5C%3Bs%7D%7B1%5C%3Bh%7D%20%5C%5C%5C%5C%0Av%3D9.072%5Cpi%5Capprox%2028.5%20%5C%3Bkm%2Fh" />.