If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is :

Answer: Option A

Let the actual distance travelled be x km
Then,
$$\begin{array}{rl}& \iff \frac{x}{10}=\frac{x+20}{14}\\ & \iff 14x=10x+200\\ & \iff 4x=200\\ & \iff x=50\text{ km}\end{array}$$