Question

A plucked string of length 1.2 m produced a note of frequency 150 Hz.
Calculate its length that will produce a note of frequency 75 Hz

Answer 1

$$v=f\lambda=2Lf=const$$

$$f_1\lambda_1=f_2\lambda_2\to (150)(1.2)=(75)l_2$$

$$l_2=0.60\ m$$