A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour ?

Answer: Option B

Speed :
$$\begin{array}{rl}& =\left(\frac{600}{5\times 60}\right)\text{ m/sec}\\ & =\text{ 2 m/sec}\\ & =\left(2\times \frac{18}{5}\right)\text{ km/hr}\\ & =\text{ 7}\text{.2 km/hr}\end{array}$$