Ahomeowner’s association monitored the number of households in a neighborhood using their sprinkler systems during certain hours. what’s the answer?

The period of a graph is the distance between 2 high points or 2 low points.

 This graph is symmetrical so the distance between the 2 high points is the same as the distance between the 2 low points.

 There is a high point at 7 p.m. and the next high point is 11 a.m.

7 p.m. to 7 a.m. is 12 hours
7a.m. to 11 a.m. is 4 hours

 12 +4 = 16 hours total