Please help me with my physics! I will choose brainliest and please provide work I don’t understand

It's nice to know all of those things about the wave in the jump rope. But if you only want to find the period of the wave, then the only thing you need to know is its frequency, because [ Period = 1 / Frequency ] .
Frequency = 2.5 Hz
Period = 1 / 2.5Hz
Period = 0.4 second