Speed of Duronto Train

Step 1: Rajdhani crosses a platform equal to its length in 36 sec.

Let length of Rajdhani = L meters ⇒ Platform = L meters ⇒ Total distance = 2L meters

Speed = 54 km/hr = 15 m/s

So, 2L = 15 × 36 = 540 ⇒ L = 270 m

Step 2: Duronto (length 230 m) crosses same platform (270 m) = total distance = 500 m

Time = 25 sec

Speed = Distance / Time = 500 / 25 = 20 m/s

Convert to km/hr: 20 × 18 / 5 = 72 km/hr

✅ Final Answer: 72 km/hr

Train Collision Problem

Navjivan Express leaves Ahmedabad at 6:30 am traveling at 50 km/h towards Baroda (100 km away).
At 7:00 am, Howrah-Ahmedabad Express leaves Baroda towards Ahmedabad at 40 km/h.
At 7:30 am, Mr. Shah realizes both trains are on the same track heading toward each other.

Step 1: Navjivan distance by 7:30 am = 50 km/h × 1 h = 50 km
Step 2: Howrah distance by 7:30 am = 40 km/h × 0.5 h = 20 km
Step 3: Distance between trains at 7:30 am = 100 − (50 + 20) = 30 km
Step 4: Relative speed = 50 + 40 = 90 km/h
Step 5: Time until collision = 30 km / 90 km/h = 1/3 hour = 20 minutes

Time to avert collision: 20 minutes