A train running at a speed of 30 metres/sec crosses a platform 600 metres long in 30 seconds. The length of t… - RRB Staff Nurse Delhi-2015

RRB Staff Nurse Delhi-2015

Reasoning

Hard

Appeared in: RRB Staff Nurse Delhi-2015

Explanation

The core principle is that the total distance a train covers when crossing a platform is the sum of its own length and the platform's length.
The total distance can be calculated using the fundamental formula: Distance = Speed × Time.
Given the speed (30 m/s) and time (30 s), the total distance the train travels is 30 × 30 = 900 meters.
To find the train's length, subtract the platform's length (600 m) from the total distance covered (900 m), which results in 300 meters (900 - 600 = 300).

Option A: This is an arbitrary incorrect value. It does not logically follow from the calculations based on the provided speed, time, and platform length.
Option B: This is another incorrect value. It may arise from a calculation error, but it does not represent the correct application of the formula.
Option C: This is an incorrect value. A possible mistake could be miscalculating the total distance or incorrectly setting up the relationship between train length, platform length, and total distance.

Visual 1: Diagram - An infographic illustrating a train crossing a platform. It should clearly label the 'Length of Train', 'Length of Platform', and the 'Total Distance Covered', visually demonstrating that the total distance is the sum of both lengths.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain This question tests the application of the concepts of speed, distance, and time, specifically in the context of problems involving trains and platforms as background academic context rather than a clinical decision trigger.
While not a clinical question, this problem tests quantitative aptitude, a key component of nursing entrance examinations.
The ability to accurately apply formulas and perform multi-step calculations is a transferable skill essential for clinical practice, such as in drug dosage calculations and IV drip rate administration.
What if the question asked for the time to cross a pole? If a train crosses a stationary object of negligible length (like a person or a pole), the distance covered is simply the length of the train itself. In that case, Time = Length of Train / Speed.

How to Approach the Question

First, identify all the given variables from the problem statement: Speed = 30 m/s, Time = 30 s, and Platform Length = 600 m.
Recognize the key concept: When a train crosses an object with significant length (like a platform), the total distance it must travel is the sum of its own length and the object's length.
Use the basic formula Distance = Speed × Time to calculate the total distance the train traveled during the crossing.
Substitute the known values: Total Distance = 30 m/s × 30 s = 900 m.
Set up the final equation: Total Distance = Length of Train + Length of Platform.
Isolate the unknown variable (Length of Train) and solve: Length of Train = 900 m - 600 m = 300 m.

Concept Tested & Keywords

Concept Tested: This question tests the application of the concepts of speed, distance, and time, specifically in the context of problems involving trains and platforms.
Stem keywords: train, speed, platform, length, time
Lead-in keywords: The length of the train is?

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