During a laboratory activity to study wave motion on a stretched string, a group of students make three separate time measurements for 20 complete oscillations of the string. Their observations are given below:
Trial 1: 25.6s
Trial 2: 25.4s
Trial 3: 25.8s
(i) For each trial, calculate the frequency of oscillation of the string.
(ii) Determine the average frequency of the string from the three trials.
(iii) Using your answer to part (ii), calculate the average time period of the string.