F = 1/T -- Observing The vibrations of a guitar string. Determine the frequency of oscillations, & Determining the frequency of oscillations.

[TimeFlipper]

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.

Harte

Of course Hartey, iam merely replying to your own posting below ..

In fact, frequency is only equal to 1/t when the wavelength is one meter, because f=L/t, not 1/t.

 

[Harte]

Of course Hartey, iam merely replying to your own posting below ..

Well, you had asked what was wrong with what you posted, and that was the only thing I saw.

Harte