GATE2019 IN: GA-9

Question

Two trains started at $7$AM from the same point. The first train travelled north at a speed of $80$km/h and the second train travelled south at a speed of $100$km/h. The time at which they were $540$ km apart is ________ AM.

• A. $9$
• B. $10$
• C. $11$
• D. $11.30$

Answer 1

The trains are traveling in opposite directions and so their relative speed is the sum of their individual speeds.

Relative speed $ = $ Speed of Train 1 + Speed of Train 2 $= 80 + 100 = 180 \; kmph$

Distance $ = 540$

Time taken $ = \frac{\text{Distnace}}{\text{Speed}} = \frac{540}{180} = 3$

So, at $7am + 3 = 10am$ the trains will be seperated by $540$ kms.

Correct Answer: B

Answer 2

Since, both trains start from a point and goes in opposite directions, first train covers 80 kms in one hour and other train covers 180 kms in an hour. So, they goes 180 kms apart in one hour. So, in 3 hours they go 540 kms apart. So, after 3 hours time will be 10am.