There are two questions here: 1st is... The velocity of sound in air is 343 m/s. A train moving away from a detector at 29 m/s blows a 350 Hz horn. What frequency is detected by a stationary train? I got the correct answer of 322.7 using dopplers equation. Now part 2 is... What frequency is detected by a train moving away from the first train at a speed of 15.6 m/s? Plugging in ----> f' = [350*343] / [343+15.6] = 334.77 It seems correct to me, but when I submitted my answer online I was incorrect. Please help! Thanks!