Multiple choice

Travelling along parallel paths in a railway track, two goods trains cross each other. The faster train, having a length of 180 metres, crosses a lamp post within a 15-second interval. Additionally, the slower train, with a speed 4 km/hr less than the faster one, crosses paths with the faster train in an 18-second interval. What is the length of the slower goods train, in meters?

  1. 192

  2. 215

  3. 232

  4. 225

  5. a
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Faster train speed v = 180/15 = 12 m/s (43.2 km/hr). Slower train speed = 43.2 - 4 = 39.2 km/hr = 10.88 m/s. Relative speed = 12 + 10.88 = 22.88 m/s. Total distance = (L1 + L2) = 22.88 * 18 = 411.84. L2 = 411.84 - 180 = 231.84, which rounds to 232.

AI explanation

The faster train speed equals its length 180 m divided by 15 s, yielding 12 m/s. The slower train speed is 4 km/hr less, converting to 10/9 m/s less, making it 98/9 m/s. The relative speed for crossing is 12 m/s plus 98/9 m/s, yielding 206/9 m/s. Using the crossing formula distance equals speed multiplied by time, the total crossing distance is 206/9 m/s multiplied by 18 s, yielding 412 m. Subtracting the faster train length of 180 m gives the slower train length of 232 m.

Keep practicing — related questions