One inlet pipe can fill an empty pool in 12 hours, and a drain can empty the pool in 20 hours. How long will it take the pipe to fill the pool if the drain is left open? Express your answer as a reduced fraction.

The answer to that is 6

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.