Answer :
herz is a measurement for how many cycles of the wave occur per second, which in this case is 261. the period is the time it takes to complete 1 cycle, so if 261 cycles occur per second, one cycle occurs every 1/261 seconds
Period = 1/frequency.
Because the frequency is 261, 1/261 = the period :)
Because the frequency is 261, 1/261 = the period :)