Assume: Take the speed of sound in air to be 343 m/s. A bat, moving at 5.9 m/s, is chasing a flying insect. The bat emits a 46 kHz chirp and receives back an echo at 46.26 kHz. At what speed is the bat gaining on its prey? Answer in units of m/s. I tried this: f=initial frequency fo=observed frequency x= velocity of insect fo/f=(343+Vbat)/(343+x) but it doesn't seem to work: 46260/46000=(343+5.9)/(343+x) 1.0056=348.9/(343+x) 343+x=346.94 x=3.939 then i take the velocity of the bat: 5.9-3.939=1.96 this answer isn't right though, but I dont see why.