The Bob of a simple pendulum takes 0.25s to swing from its equilibrium position to one extreme. calculate it's period

Hence the period is 1 sec.

Explanation:

If the time taken by a single pendulum is 0.25 seconds. Then a pendulum will move to two extreme positions from one mean position only. That will means that the total time period is given by

                             T = 2 0.25 = 0.50 seconds.

A pendulum will oscillate from mean to the extreme, then extreme to mean, then mean to the extreme and again extreme to mean, so it will cover 2 cycles.

                                   Hence, 2 0.50 = 1.