A sound wave travels a distance 1020 m in 5 minutes. If the length of the three successive crests is 15 m, then calculate the wave speed.

Question

"Length of three crests"? I'm not sure about that. Is the question okay? I'm confused. :/

Answer 1

three crests span two complete waves.
Think of a sine wave. max-max is one wavelength, so max-max-max is two wavelengths.

So, the wavelength is 7.5m

Now use your formula: speed = wavelength * frequency