Answer:
The approximate diameter of the mirror is;
[tex]20\text{ inches}[/tex]Explanation:
Given that the length of ribbon that is enough to go round the circular mirror once is 63 inches which is equal to the circumference of the mirror.
[tex]C=63\text{ inches}[/tex]Recall that the formula for the circumference of a circle is;
[tex]\begin{gathered} C=2\pi r \\ C=\pi d \\ d=\frac{C}{\pi} \\ \text{where;} \\ C=\text{circumference} \\ r=\text{radius} \\ d=\text{diameter} \end{gathered}[/tex]Substituting the value of C to calculate d;
[tex]\begin{gathered} d=\frac{C}{\pi}=\frac{63}{\pi}\text{ inches} \\ d=20.05\text{ inches} \\ d\approx20\text{ inches} \end{gathered}[/tex]Therefore, the approximate diameter of the mirror is;
[tex]20\text{ inches}[/tex]