A siren has a frequency of 875 Hz when it and an observer are both at rest. The observer then starts to move and finds that the frequency he hears is 1251 Hz.
(a) Is the observer moving toward or away from the siren?
1)The observer is moving away from the siren
2)The observer is moving toward the siren
(b) What is the speed of the observer? (Use 343m/s as the speed of sound).