1. The problem statement, all variables and given/known data As you drive at a speed of 15.0 m/s an ambulance approaches you from behind with its siren blaring at a frequency of 1022 Hz. After the ambulance has passed you the signal is now 981 Hz. If both you and the ambulance travel at a constant speed how fast was the ambulance traveling? A. 16.0 m/s B. 18.0 m/s C. 20.0 m/s D. 22.0 m/s E. 24.0 m/s 2. Relevant equations f0=fs(1/(1+vs/v)) 3. The attempt at a solution I figured I could use the ambulance's speed relative to the car, so I used the above equation for when a source is moving away from a stationary observer. I plugged in all the variables an solved for vs. I ended up getting vs being equal to 14.33. I then assumed since the speed was calculated with the car having a speed of 0 m/s, I simply added the speed of the car. That got me 29.33 m/s, which doesn't happen to be an answer choice. What am I doing wrong? Thank you so much!