When a pendulum clock gains time, what adjustiment should be made?

when a pendulum clock gains time , what adjustments should be made ?

When does a pendulum clock gain time ? When does it lose time ? Explain with reference to effective length.

When pendulum clock is running fast, what should be done for adjust the true time?

Will a pendulum clock gain or lose time when take to the top of a mountain?

Will a pendulum clock lose or gain time when taken to the top of a mountain?

Will a pendulum clock lose or gain time when taken to the top of a mountain ?

Will pendulum clock lose or gain time on hills or inside the mines ?

A pendulum clock runs 20s slow per day. What should be the change in length of the clock so that it records correct time? Take the pendulum as a simple pendulum.