Problems on waves

S17 A fisherman notices that wave crests pass the bow of his anchored boat every 3.0 seconds. He measures the distance between two crests to be 7.5 meters. How fast are the waves traveling?

S18 The A key above "Middle C" on the piano produces a sound wave with a frequency of 440 Hz. The speed of sound in air at room temperature is 344 m/s. What is the wavelength of the sound waves associated with middle C?