GATE CS 2019 QGA-3 — General Aptitude

Since both cars start from the same location at the same time and travel in the same direction, we can use the concept of relative speed.

Let:

• Speed of the first car, $v_1 = 50\text{ km/h}$
• Speed of the second car, $v_2 = 60\text{ km/h}$

The relative speed of the second car with respect to the first car is:

This means the distance between the two cars increases at a rate of $10\text{ km}$ every hour.

To find the time ($t$) required for the distance between them to be $20\text{ km}$:

Thus, it takes $2$ hours for the distance between the two cars to be $20\text{ km}$.