Physics Help, Multiple Problems!!!?

[van86882]

How many beats will be heard if two identical flutes each try to play middle C (262 Hz), but one is at 3.5°C and the other at 31.0°C? Assume that the warmer flute plays the pitch correctly.
_______ beats/sec

At the Indianapolis 500, you can measure the speed of cars just by listening to the difference in pitch of the engine noise between approaching and receding cars. Suppose the sound of a certain car drops by a factor of 1.50 as it goes by on the straightaway. How fast is it going? (Take the speed of sound to be 343 m/s.)
_____ km/h

Two loudspeakers are 2.5 m apart. A person stands 2.9 m from one speaker and 4.4 m from the other. Let T = 20°C.
(a) What is the lowest frequency at which destructive interference will occur at this point?
_____ Hz
(b) Calculate two other frequencies that also result in destructive interference at this point (give the next two lowest).
second lowest frequency
_____ Hz
third lowest frequency
____ Hz