ANSWER:
155.7 Hz
STEP-BY-STEP EXPLANATION:
We have that the formula between length and frequency is as follows:
[tex]\begin{gathered} \frac{L_2}{L_1}=\sqrt[]{\frac{F_1}{F_2}} \\ L_1=0.75\text{ m} \\ L_2=0.95\text{ m} \\ F_1=250\text{ Hz} \\ \text{ Replacing:} \\ \frac{0.95}{0.75}=\sqrt[]{\frac{250}{F_2}} \\ 1.267=\frac{\: 15.81}{\sqrt[]{F_2}} \\ \sqrt[]{F_2}=\frac{15.81}{1.267} \\ F_2=\mleft(\frac{15.81}{1.267}\mright)^2 \\ F_2=155.7\text{ Hz} \end{gathered}[/tex]The frequency of the second string is 155.7 Hz
