Multiple choice

A train crosses a tunnel half of its length with speed of 72 km/hr in 1 min. If train running with 50% of its speed, then find in how much time it will cross another train, which length is twice its length and standing on a platform?

  1. 4 min

  2. 5 min

  3. 7 min

  4. 6 min

  5. 8 min
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The train speed is 1200 m/min, and the tunnel is half the train's length, so the first crossing distance is 1.5 times the train length. At half speed, the train travels 600 m/min, and crossing a stationary train twice its length requires covering three train lengths. The required time is 4 minutes.

AI explanation

Let the length of the train be L, so the tunnel's length is L/2. The train runs at 72 km/hr, which converts to 20 m/s, and crosses the tunnel in 1 min, or 60 seconds. The total distance covered is the train length plus the tunnel length, calculated as 20 multiplied by 60 equals 1200 meters. This means L + L/2 = 1200, so 1.5L equals 1200 and L equals 800 meters. The new speed is 50% of 72 km/hr, which is 36 km/hr or 10 m/s. The train crosses another train of twice its length standing on a platform, meaning the other train's length is 1600 meters. The total distance to cover is 800 plus 1600, equaling 2400 meters. The required time is 2400 divided by 10, which is 240 seconds or 4 minutes.

Keep practicing — related questions