Of course Hartey, iam merely replying to your own posting below ..What you wrote is true only for waves traveling at the speed of light. The thread is about a guitar string.
Speed of a wave on a string under tension:
View attachment 12387
Here, FT is the tension in the string, and mu is the string's mass (per unit length.)
Obviously, it would be easier to calculate (and to understand) this speed using the frequency vs. wavelength method.
In fact, frequency is only equal to 1/t when the wavelength is one meter, because f=L/t, not 1/t.