Question
A train travelling at the speed of 72 km/hr crosses
another train, having 60 meters less length and travelling in opposite direction at the speed of 54 km/hr in 6 seconds. If the longer train crosses a platform in 12 seconds, then the shorter train will cross the same platform in how many seconds?Solution
Speed of longer train = 72 Γ (5/18) = 20 m/s
Speed of shorter train = 54 Γ (5/18) = 15 m/s
Let length of longer and shorter trains be βLβ meters and (L β 60) metres, respectively.
According to question,
L + L β 60 = (20 + 15) Γ 6 = 210
2L β 60 = 210
L = 135 metres
So, L β 60 = 75 metres
Let length of platform is βPβ metres
So, P + 135 = 20 Γ 12 = 240
P = 240 β 135 = 105 meters
Desired time = (105 + 75)/15 = 180/15 = 12 seconds
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