Complex Sound Waves

[Angie913]

There's this problem I'm having lots of trouble with. It is:
A person hums into the top of a well and finds that the standing waves are established at frequencies of 48, 80, and 112 Hz. The freq. of 48 Hz is not necessarily the fundamental freq. The speed of sound is 343m/s. How deep is the well?
I'm not sure where to start! The only equations we have for height are:
h=.5gt^2
and
h=velocitysound(t2-t1) which doesn't help!! I'm not sure what I should use. Any hints are great! Thanks

[Hurkyl]

Okay, if you're lost when considering height, then try looking at the other parts of the problem.

[Gamma]

Consider the relationship between wavelength and length of a one side closed tube. You may have to assume that the given frequencies corresponds to three consecutive harmonics (n, n+1 and n+2)