If the time shown by a wall clock is 12:40 AM/PM then what will be the apparent time as shown by its mirror image?

Appeared in: AIIMS Manglagiri NO - 2019

Explanation

The fundamental rule for finding the mirror image of a clock is that the sum of the actual time and the mirror time is 12:00.
To calculate the mirror time, subtract the given time from 12:00. For easier subtraction, 12:00 can be written as 11:60.
A special case exists for times with the hour 12 (e.g., 12:40). In this situation, the hour '12' is treated as '00' for the calculation.
Calculation: 11:60 - 00:40 results in 11:20.
Visually, at 12:40, the minute hand is at the '8'. Its mirror image would be at the '4', which corresponds to 20 minutes. The hour hand is just past '12', so its reflection would be just before '12', confirming the time is 11:20.

Option B: This is an incorrect calculation. It might result from incorrectly subtracting the minutes (e.g., 60 - 40 = 20) but failing to adjust the hour correctly.
Option C: This is a duplicate of option B and is also incorrect for the same reasons.
Option D: This is the original time given in the question, not its reflection in a mirror.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Logical Reasoning: Clock and Mirror Images as background academic context rather than a clinical decision trigger.
While not a direct clinical skill, aptitude tests including logical reasoning are often part of the selection process for nursing programs and jobs.
Strong problem-solving and logical reasoning skills are essential for nurses in clinical practice for tasks like interpreting data, prioritizing care, and troubleshooting equipment.
These skills help in making quick, accurate decisions under pressure, which is a daily reality in the nursing profession.

How to Approach the Question

Identify the question type: This is a logical reasoning problem involving a clock's mirror image.
Recall the key formula: Mirror Image Time = 12:00 - Actual Time.
For easier calculation, rewrite the formula as: Mirror Image Time = 11:60 - Actual Time.
Identify any special conditions. The time given is 12:40. For times involving '12' as the hour, treat '12' as '00' in the calculation.
Apply the formula: Subtract 00:40 from 11:60.
Calculate the result: 11:60 - 00:40 = 11:20.

Concept Tested & Keywords

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Practise the full AIIMS Manglagiri NO - 2019

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