To find out how long a single period of time takes, you have to divide the six seconds by the five time periods.
6/5 = 1.2 seconds
When the church clock chimes twelve o`clock, there are eleven periods in between. Therefore, you have to calculate:
11 x time period
11 x 1.2 seconds = 13.2 seconds
Answer: At twelve o`clock, the bells of the church clock chime for 13.2 seconds.