math
posted by confused .
A woman is sitting in a boat at anchor on a lake. Her boat bobs up and down once every 2.0·s. She notices that when the front of her 3.0·m long boat is at one wave crest, a second crest is at the middle of her boat, and a third is at the end.
What is the frequency of the waves?

It doesn't matter how long her boat is. The boat bobs up and down every 2 seconds. In that time, two wave fronts have passed. So, the frequency is 2waves/2sec = 1/sec = 1 Hz.

Damon got it right.
The two wave fronts means that the boat has bobbed twice by the time they have passed, but it only bobs once in 2 seconds. So, frequency is indeed 1/2 Hz