Multiple choice

Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?

  1. 23 m
  2. $23 \dfrac{2}{9}$
  3. $27 \dfrac{7}{9}$

  4. 29 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative speed = 40 - 20 = 20 km/hr = 20 * (5/18) m/s = 100/18 = 50/9 m/s. Length = Speed * Time = (50/9) * 5 = 250/9 = 27 7/9 m.

AI explanation

Because both trains move in the same direction, the relative speed is 40 km/hr minus 20 km/hr, which equals 20 km/hr. Multiplying by 5/18 gives the relative speed in m/s as 50/9 m/s. The fast train completely passes the man in 5 seconds, so its length is the relative speed multiplied by the time: (50/9 m/s) times 5 s equals 250/9 m, which is 27 7/9 m.

Keep practicing — related questions