A train is running with a speed of 90 km/hr. If the length of the train is 400 meters, how much time will it take to cross a bridge of 200 meters length?

1. A

   20 sec

2. B

   22 sec

3. C

   24 sec

4. D

   26 sec

Appeared in: KGMU 2023

Explanation

• The first step is to calculate the total distance the train needs to cover to fully pass the bridge. This is the sum of the train's length and the bridge's length (400 m + 200 m = 600 m).
• The second step is to convert the train's speed from km/hr to m/s to match the units of distance. 90 km/hr is equivalent to 90 * (5/18) = 25 m/s.
• The final step is to calculate the time using the formula Time = Distance / Speed. Plugging in the values gives Time = 600 m / 25 m/s = 24 seconds.

Why Other Options Were Wrong

• Option A: This answer (20 seconds) would be obtained if the speed was incorrectly calculated as 30 m/s (600 / 30 = 20) or if the total distance was incorrectly assumed to be 500 m (500 / 25 = 20).
• Option B: This answer (22 seconds) results from a miscalculation. With a total distance of 600 m, a time of 22 seconds would imply a speed of approximately 27.27 m/s, which is incorrect.
• Option D: This answer (26 seconds) results from a miscalculation. With a total distance of 600 m, a time of 26 seconds would imply a speed of approximately 23.08 m/s, which is incorrect.

Related Visual

• Visual 1: Infographic: Visualizing Total Distance. An image showing the train at the point of entering the bridge and at the point where its rear has just left the bridge, illustrating that the total distance covered is (Length of Train + Length of Bridge).

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Time, Speed, and Distance as background academic context rather than a clinical decision trigger.
• This is a general aptitude question testing mathematical reasoning.
• It does not have direct clinical or nursing relevance but assesses the basic numeracy skills required in many professional fields.
• What if? - If the stem changed one defining clue so that 24 sec no longer matched, reassess the option whose mechanism, classification, or indication now fits the revised presentation.

How to Approach the Question

• First, identify all the given values: speed of the train, length of the train, and length of the bridge.
• Recognize that for the train to 'cross' the bridge, its entire length must pass over the bridge's entire length. Therefore, calculate the total distance by adding the length of the train and the length of the bridge.
• Check the units. The speed is in km/hr, while the lengths are in meters. Convert the speed to m/s for consistency by multiplying by 5/18.
• Apply the fundamental formula: Time = Distance / Speed.
• Perform the final calculation to find the time in seconds.

Concept Tested & Keywords

• Concept Tested: Time, Speed, and Distance
• Stem keywords: train, speed, 90 km/hr, length, 400 meters, bridge, 200 meters
• Lead-in keywords: how much time

Question ID

Q4s3j9yRQ3MHcgOC3W7d0G

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