Navjivan
Express from Ahmedabad to Chennai leaves Ahmedabad at 6.30 a.m. and travels at
50 kmph
towards Baroda situated 100 km away. At 7.00 a.m. Howrah- Ahmedabad Express
leaves Baroda towards Ahmedabad and travels at 40 kmph.
At 7.30 a.m. Mr
Shah, the traffic controller at Baroda realizes that both the trains are
running on the same track. How much time does he have to avert a head-on
collision between the two trains?
The distance between Ahmedabad and
Baroda is 100 Km Navjivan
express starts at 6:30 am at 50 Km/hr
and Howrah expresses starts at 7:00 am at 40 Km/hr.
Distance covered by Navjivan
express in 30 minutes (by 7 am) is 25 Km/hr.
So, at 7 am, the distance between the two trains is 75 Kms
and they are travelling towards each other a relative speed of 50+40-90
Km/hr.
So, time taken them to meet is 75/90*60 = 50 minutes.
As, Mr. Shah realizes the problem after thirty minutes, time left to avoid
collision is 50-30 = 20 minutes