Answer: 54.88 mph
Step-by-step explanation: the Doppler effect formulae is given below as
f' = (v + vo) /(v - vs) × f
Where f' = observed frequency = 236 Hz,
f = frequency of sound source (stationary frequency) = 253 Hz.
v = speed of sound in air = 761 mph
Since the car (source) is moving away relative to the observer, vs will have a negative value (-vs)
vo = 0 mph ( since the observer is not moving)
By substituting the parameters, we have that
236 = (761+0)/(761 - (-vs)) × 253
236 = (761/ 761 +vs) × 253
By cross multiplication, we have that
236 × (761 +vs) = 761 ×253
761 + vs = 761 ×253/ 236
761 + vs = 192533/ 236
761 + vs = 815.88
vs = 815.88 - 761
vs = 54.88 mph
12.900 because it is only one digit away from the next hundred
Check the picture below, the graphs of f(x) and g(x) are on the right-side.
