It takes 15 seconds for a train travelling at 60 km/hour to cross entirely another train half its length and travelling in opposite direction at 48 km/hour. It also passes a bridge in 51 seconds. The length of the bridge is
Explanation:
Relative speed of the longer train with respect to the
shorter one = (60 + 48) × 518 = 30 m/s
Let the length of the longer train be x m.
Now the distance travelled by the longer train to cross the shorter train = length of the longer train + length of the shorter train = x + x/2 = 3x/2
The trains cross each other with a speed of (60 + 48) km/h
(60 + 48) km/h = (60 + 48) × 518 = 30 m/s
Therefore,
3x2 = 30 × 15
∴ x = 300 mts
Let the length of the bridge be L.
Now total distance covered in crossing the bridge
= length of the longer train + length of the bridge
= 300 + L
∴ 300 + L = 60 × 518 × 51 = 850
∴ L = 550 mts
Hence, option (a).
Help us build a Free and Comprehensive Preparation portal for various competitive exams by providing us your valuable feedback about Apti4All and how it can be improved.