The Doppler effect causes a sound moving towards you to sound higher pitched and a sound moving away from you to sound lower pitched, like observed in listening to the car horn in the video.

When the source of the sound is moving away from the observer, the equation that describes this phenomenon is $\displaystyle {f}={\left(\frac{{c}}{{{c}+{v}}}\right)}{f}_{{0}}$, where
f is the observed frequency (pitch) of the sound, in Hertz
c is the speed of sound, in miles per hour (about 761 miles per hour)
v is the speed of the sound source, in this case the car, in miles per hour
f₀ is the frequency of the sound when stationary

Using a spectrum analyzer, we could determine the observed frequency when the car was driving towards us was 266 Hz and the frequency while driving away was 238 Hz, suggesting a stationary frequency of 252 Hz.

Use this information and the equation to estimate the speed of the car in miles/hour. Round your answer to one decimal place.

mi/hr