UPSC CSE Prelims 2015
To determine the time when the minute hand is 3 minutes ahead of the hour hand between 6 p.m. and 7 p.m., we calculate the relative positions and speeds of the clock hands.
At 6:00 p.m., the hour hand is at the 6-mark (180 degrees from the 12-mark), and the minute hand is at the 12-mark (0 degrees). The hour hand is initially 180 degrees ahead of the minute hand.
For the minute hand to be 3 minutes ahead of the hour hand, it needs to cover the initial 180-degree gap and then move an additional 3 minutes (which is 3 × 6 = 18 degrees) ahead of the hour hand's current position.
Let 't' be the number of minutes past 6:00 p.m.
We set up the equation where the minute hand's angle is 18 degrees greater than the hour hand's angle:
6t = (180 + 0.5t) + 18
6t = 198 + 0.5t
5.5t = 198
t = 198 / 5.5
t = 36 minutes
Therefore, at 6:36 p.m., the minute hand will be 3 minutes ahead of the hour hand.
The positions of the hands for the other options do not satisfy the given condition:
Thus, options A, B, and D are incorrect as they do not correspond to the minute hand being 3 minutes ahead of the hour hand.