You are watching a marching band practice outdoors. Near you are two trumpet players, one marching directly towards you and one away from you at the same speed. Each trumpet player is playing an A (440 Hz) and you hear a beat between the two sounds at a frequency of 2 Hz. How fast are the trumpet players marching in m/s?

Details and assumptions
The speed of sound is 340 m/s.
The trumpet players aren't moving very fast.

4 answers

0.733

it's wrong

the answer is 0.77

@Anonymous is right, the correct given answer is 0.773. Given by nSolve(440/(1 - x/343) = 442, x) / 2