A man can cover a certain distance in 3 hours 36 minutes If he walks at the rate of 5 km/hr. If he covers the same distance on cycle at the rate of 24 km/hr, then the time taken by him in minutes is :

Answer: Option B

Total distance covered by man in 3 hours 36 minutes is :
$$\begin{array}{rl}& =5\times 3\frac{36}{60}=5\times 3\frac{3}{5}\\ & =5\times \frac{18}{5}\\ & =18\text{ km}\end{array}$$
18 km is covered at an speed of 24 km/hr
∴ Time taken is :
$$\begin{array}{rl}& =\frac{18}{24}\\ & =\frac{3}{4}\times 60\\ & =45\text{ minutes}\end{array}$$