You are riding your bicycle directly away from a stationary source of sound and hear a frequency that is 2.5% lower than the emitted frequency. The speed of sound at the temperature that day is 339 m/s. What is your speed?
f = f0(v + vo)/v.
Here, vo is the unknown. f = fo*.985
V is 339
1+vo/339 = .985
vo/330=-.025
solve for vo. the negative sign means moving away.