1. The problem statement, all variables and given/known data The pitch of the sound from a racecar engine drops the musical interval of a fourth when it passes the spectators. This means the frequency of the sound after passing is 0.75 times what it was before. How fast is the racecar moving? 1. 61 m/s 2. 49 m/s 3. 72 m/s 4. 68 m/s 2. Relevant equations fo = fs / 1 - (vs/v) 3. The attempt at a solution I tried using 75 = 100 / (1 - (vs/331) to solve for the speed of the source, but my answer was way off...there's got to be something i'm missing. am i correct in thinking i need to use v = 331 for the speed of sound? then what do i use for fo and fs?