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Mathematics
Speed, Time and Distance
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RRB NTPC Graduate Tier 1 2025 Shift-1 📅 06 May, 2025

A train running at a speed of 72 km/hr crosses a stationary pole in 15 seconds. What is the length of the train (in metres)?

A
250
B
300
C
350
D
400
Result Summary
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RRB NTPC Graduate Tier 1
2025 • 06 May, 2025 • Shift-1
A train running at a speed of 72 km/hr crosses a stationary pole in 15 seconds. What is the length of the train (in metres)?
Correct Answer
300
Unit Standardization: The speed is provided in km/hr, but the crossing time is given in seconds. We must first establish unit consistency by converting the spee......
Ref/Book : RRB NTPC Graduate Tier 1 2025
Ref. Subject Mathematics
Chapter -
Ref. Topic Speed, Time and Distance
Pg. No -
💡 Analysis & Explanation
Unit Standardization ▼
The speed is provided in km/hr, but the crossing time is given in seconds. We must first establish unit consistency by converting the speed to m/s.
Conversion Process ▼
To convert km/hr to m/s, multiply the value by the standard conversion factor of 5/18. Therefore, 72 × (5/18) precisely equals 20 m/s.
Distance Logic ▼
When a train completely crosses a point object like a pole, the physical distance it covers is exactly equal to its own longitudinal length.
Final Calculation ▼
Using the fundamental formula Distance = Speed × Time, we multiply the converted speed by the given time: 20 m/s × 15 s = 300 metres.
Conclusion ▼
The total length of the train is 300 metres.
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