Multiple choice

A train with a uniform speed passes a platform, 122 m. long, in 17 sec and a bridge 210 meters long in 25 seconds.Find the speed of the train. एक ट्रेन 122 मी.लम्बा प्लेटफार्म 17 सेकंड में और 210 मी. लम्बा पुल 25 सेकंड में पार करती हैं। ट्रेन की चाल ज्ञात कीजिये।

  1. 37.6 km/hr. / किमी/घंटा

  2. 41.5 km/hr. / किमी/घंटा

  3. 46.5 km/hr. / किमी/घंटा

  4. 39.6 km/hr. / किमी/घंटा
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D Correct answer
Explanation

Let train length = L meters and speed = S m/s. Speed = (L + platform length)/time, so S = (L + 122)/17 = (L + 210)/25. Cross-multiplying: 25(L + 122) = 17(L + 210), giving 25L + 3050 = 17L + 3570, so 8L = 520 and L = 65m. Speed = (65 + 122)/17 = 187/17 m/s. Converting to km/hr: (187/17) × (3600/1000) = 39.6 km/hr.

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