Two trains, P and Q, are running on parallel tracks in opposite directions with lengths of 110 m and 140 m, respectively. Train P is running at a speed of 70 km/h and took 5 seconds to cross train Q. The speed of train Q is:
Show answer & explanation
Correct answer: C
Explanation
The corret answeris option 3 i.e 110 km/h.
Let the speed of train Q be x km/h.
Relative Speed:
Since the trains are moving in opposite directions, their relative speed is the sum of their individual speeds: 70 + x km/h.
Converting km/h to m/s:
70 km/h = (70 × 1000) / 3600 = 19.44 m/s
x km/h = (x × 1000) / 3600 = (5x/18) m/s
Total Distance Covered:
The total distance covered by both trains in 5 seconds is the sum of their lengths: 110 + 140 = 250 meters.
Using the formula: Distance = Speed × Time
250 = (19.44 + 5x/18) × 5
Solving for x:
250 = 97.2 + (25x/18)
152.8 = 25x/18
x = (152.8 × 18) / 25
x = 110.112
Therefore, the speed of train Q is approximately 110 km/h.