A train is travelling at a rate of 90 km/hr. How many seconds, it will take to cover a distance of 4/5 km?

Appeared in: DHS Staff Nurse - 2018 (Shift-2nd)

Explanation

The core relationship is Time = Distance / Speed.
The speed is given as 90 km/hr, and the distance is 4/5 km (or 0.8 km).
First, calculate the time in hours: Time = (4/5) / 90 = 4 / (5 * 90) = 4/450 hours.
To find the time in seconds, convert hours to seconds by multiplying by 3600 (since 1 hour = 3600 seconds).
Time in seconds = (4/450) * 3600.
Simplifying the calculation: (4 * 3600) / 450 = (4 * 8) = 32 seconds.

Option A: This is an incorrect calculation. It might result from misremembering the conversion factor or an arithmetic error, such as incorrectly simplifying the fraction (e.g., 3600/90 = 40, then 40 * 4/5 = 32, but maybe a mistake was made here).
Option C: This value represents the speed of the train in km/hr, not the time taken. It's a common mistake to select a number given in the problem statement without performing the necessary calculation.
Option D: This is an incorrect calculation, likely stemming from an error in unit conversion. For instance, if one incorrectly calculated time in minutes (0.8 km / 90 km/hr * 60 min/hr ≈ 0.53 min) and then made another error.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of time based on speed and distance as background academic context rather than a clinical decision trigger.
While not a clinical question, this type of calculation tests basic numeracy and problem-solving skills, which are essential for nurses.
Nurses frequently perform calculations for drug dosages, IV drip rates, and fluid balance, which require similar attention to units and formulas.
What if the distance was 4.5 km? The time taken would be Distance/Speed = 4.5 km / 90 km/hr = 0.05 hours. In seconds, this is 0.05 * 3600 = 180 seconds.

How to Approach the Question

First, identify the given information: Speed = 90 km/hr and Distance = 4/5 km.
Next, identify what the question is asking for: Time in seconds.
Recognize that the units are not consistent for the final answer (speed is in hours, but the answer must be in seconds). Decide on a unit conversion strategy.
Apply the fundamental formula: Time = Distance / Speed.
Calculate the time in hours: Time = (4/5) / 90 = 4/450 hours.
Convert the final answer from hours to seconds by multiplying by 3600. This gives (4/450) * 3600 = 32 seconds.

Concept Tested & Keywords

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Practise the full DHS Staff Nurse - 2018 (Shift-2nd)

Attempt every question from this paper in a timed mock, then review the full solution for each one.