With an average speed of 50 km/hr, a train reaches its destination in time. If it goes with an average speed of 40 km/hr, it is late by 24 min. The total journey is :

Answer: Option D

Difference between timings = 24 min = $$\frac{24}{60}$$ hr = $$\frac{2}{5}$$ hr
Let the length of the journey be x km
Then,
$$\begin{array}{rl}& \iff \frac{x}{40}-\frac{x}{50}=\frac{2}{5}\\ & \iff \frac{x}{200}=\frac{2}{5}\\ & \iff x=\left(\frac{2}{5}\times 200\right)\\ & \iff x=80\text{ km}\end{array}$$