Q.
After how much time a pendulum clock will indicate the correct time again? if it with a 12 hour dial happens to gain 1 min/day. (After setting the clock to the correct time)
The clock shows the correct time after 12 hour. The total time gained by the pendulum clock can be given by, T=12×60=720 minutes.
Since gain is 1 min/day; hence 720 days the pendulum clock will indicate the correct time again.