RAS question
A clock seen in a mirror shows 8:20. What is the actual time?
Correct answer: (D) 3:40.
If a clock appears as 8:20 in a mirror, the actual time is 3:40.
Explanation
A mirror reading of an analogue clock must be converted by reversing the displayed time across the 12-hour dial. NCERT explains the underlying optical idea: a plane mirror forms an image that is laterally inverted, so the clock face seen in the mirror is not the actual orientation of the hands. For mirror-clock questions, when the displayed minutes are more than zero, subtract the mirror time from 11:60. Here, 11:60 minus 8:20 gives 3:40. That makes 3:40 the actual time, while the apparent 8:20 is only the laterally inverted mirror image.
Why the other options are wrong
- (A) 4:20 keeps the minutes unchanged and does not follow the mirror-clock subtraction 11:60 - 8:20.
- (B) 4:40 reverses only part of the display; subtracting 8:20 from 11:60 gives 3:40, not 4:40.
- (C) 3:20 matches neither the hour nor the minute result after applying the mirror-time rule to 8:20.
Concept
This tests mirror-image reasoning in Reasoning & Mental Ability, especially lateral inversion on an analogue clock face. It recurs in RAS practice because the method is short, mechanical and easy to confuse under exam pressure.