Question

A speaker vibrates at a frequency of 200 hz what is its period

Answer 1

Period T =  1/ f               where f = frequency  in Hz, T is in seconds.

Period T =  1/200 = 0.005 seconds.

Answer 2

Period = (1) / (frequency)

Period = (1) / (200 per second)  =  0.005 second  =  5 milliseconds