# Speed of a wave

Pepe and Alfredo are resting on an offshore raft after a swim. They estimate that 3.0 m separates a trough and an adjacent crest of surface waves on the lake. They count 15 crests that pass by the raft in 19.5 s. Calculate how fast the waves are moving.

[I tried saying that frequency= 15/19.5=.769

V=f(3)

=(.769)(3)

=2.31 ] and that was wrong

Please advise me as to where my mistake is.

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Supplemented with graph, the solution shows detailed calculation of the speed of a wave.

$2.19