GATE CS 2019 Q.3 (GA Q.3): Quantitative Aptitude

Two cars start at the same time from the same location and go in the same direction. The speed of the first car is $50\text{ km/h}$ and the speed of the second car is $60\text{ km/h}$ . The number of hours it takes for the distance between the two cars to be $20\text{ km}$ is _____.

Official answer and solution

Official answer: B
From: Official GATE 2019 answer key

Solution

Use the concept of relative speed for objects moving in the same direction.

Both cars start from the same location at the same time and travel in the same direction. Let the speed of the first car be $v_1 = 50\text{ km/h}$ and that of the second car be $v_2 = 60\text{ km/h}$ .

The relative speed between the two cars is:

v_{\text{rel}} = v_2 - v_1 = 60 - 50 = 10\text{ km/h}

The time required for the distance between them to become $d = 20\text{ km}$ is:

t = \frac{d}{v_{\text{rel}}} = \frac{20\text{ km}}{10\text{ km/h}} = 2\text{ hours}

Final answer

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2019 Computer Science and Information Technology (CS)
Question: 3 of 65, printed as GA Q.3
Section: General Aptitude

Report an error in this question

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.

Question

Solution

Source