A running man crosses a bridge of length 500 meters in 4 minutes. At what speed he is running?

7.5 Km/hr

Speed = \(\frac{ Distance}{ Time}\)

Speed = \(\frac{500}{ 240}\) x \(\frac{18 }{ 5}\)

Speed = 7.5 km/hr

*Note* 

In order to convert km/hr to m/s - multiply by  \(\frac{ 5}{ 18}\)

In order to convert m/s to kn/hr - multiply by  \(\frac{ 18}{ 5}\)