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

Answer: Option B

$$\begin{array}{rl}& \text{Speed}=\frac{600}{5\times 60}\text{ m/sec}=2\text{m/sec}\\ & \text{Converting}\text{m/sec}\text{to}\text{km/hr}\\ & =2\times \frac{18}{5}\text{ km/hr}\\ & =7.2\text{ km/hr}\end{array}$$