If a train runs at 40 kmph, it reaches its destination late by 11 minutes but if it runs at 50 kmph, it is late by 5 min only. The correct time for the train to complete its journey is :

Answer: Option C

Let the correct time to complete the journey be x min
Distance covered in (x + 11) min at 40 kmph
= Distance covered in (x + 5) min at 50 kmph
$$\begin{array}{rl}& \therefore \frac{\left(x+11\right)}{60}\times 40=\frac{\left(x+5\right)}{60}\times 50\\ & \iff x=19\text{ min}\end{array}$$