Question
Two trains ‘T8’ and ‘U8’ of lengths 600 metres and
300 metres respectively are travelling towards each other. Ratio of speed of ‘T8’ to ‘U8’ is 3:2. If the trains take 36 seconds to cross each other from the time they meet, then find the average of speeds (in km/h) of trains ‘T8’ and ‘U8’.Solution
Let the speed of ‘T8’ and ‘U8’ be ‘3y’ and ‘2y’ m/s respectively.
Relative speed = 3y + 2y = 5y m/s
ATQ,
5y × 36 = 600 + 300
⇒ 180y = 900
⇒ y = 5
Therefore, required average = (3y + 2y) ÷ 2 = 2.5y
= 2.5 × 5 = 12.5 m/s = 12.5 × (18/5) = 45 km/h
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