How, using a Ripple Tank with a Signal Generator attached to the Dipper, can you find the Wave Speed?

-First get a Pencil, A Friend and a Stopwatch -Have a Large Piece of Paper next to the Tank -As the Waves move across, have one of you Track the Path of one of the Crests on the Paper, using the Pencil -The other Person should use the Stopwatch and Record how long you have been Drawing for. -Get the Speed by getting the Length of the Line and putting it in this Formula: Distance = Speed x Time