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**APPROACHES**a ringing crossing gate, Stacy, a passenger on the train, hears a frequency of 440 Hz from the bell. As the train

**RECEDES**, she hears a frequency of 410 Hz. How fast is the train traveling? (formula: f = fo (v+ vo)/(v-vs))

f= frequency that she hears

fo= actual frequency

v= 330 m/s

vo= observer's frequency

vs= source's frequency

***Solve:

f1= 440 Hz (frequency that she hears as the train approaches the ringing gate)

f2= 410 Hz (frequency that she hears as the train approaches the ringing gate)

vs= 0 m/s

v= 330 m/s

vo=?

vo= [f1(v-vs)]/fo - v

As I got to this point, I was stuck b/c there was no fo, which is the actual frequency, so that I can plug into the equation. plz show me how to do this problem...Thanks