**A student knows that an ambulance siren has a frequency of = 392 Hz. He measures, when the ambulance is approaching him, the frequency = 412 Hz. Assume the speed of sound is 343 m/s in this problem.**

**Answer:**

**A student knows that an ambulance siren has a frequency of = 392 Hz. He measures, when the ambulance is approaching him, the frequency = 412 Hz. Assume the speed of sound is 343 m/s in this problem.**

**Answer:**