How to Cut Metal to Produce Specific Musical Notes?

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Homework Statement

What I want to do is have a piece of metal, then determine the length to cut it to produce the note Middle C, and so on for an octave (exclude sharps and flats). So pretty much a xylophone made from scratch.

Homework Equations

v = f(lambda)

The Attempt at a Solution

I just randomly cut the metal, and it sounds nowhere near the real notes I'm trying to achieve. I know I need to find out the wavelength, but I have no idea how to calculate the frequency without a frequency meter.

 

[member 553083]

I have a calculator, but I don't know how to use it to calculate the wavelength/frequency. Any help would be greatly appreciated.