Step1; Draw the Diagram
From the diagram, we can see a right-angle triangle
Using Pythagoras theorem
[tex]\begin{gathered} \text{hypotenues}^2=\text{opposite}^2+\text{adjacent}^2 \\ \text{hypotenues}=22.5\operatorname{mm} \\ \text{opposite}=18\operatorname{mm} \\ \text{adjacent}=r \end{gathered}[/tex]
hence we have
[tex]\begin{gathered} 22.5^2=18^2+r^2 \\ r^2=22.5^2-18^2 \\ r^2=182.25 \\ r=\sqrt[]{182.25} \\ r=13.5\operatorname{mm} \end{gathered}[/tex]
Hence the radius of circle C is 13.5mm
[tex]\begin{gathered} \text{diameter}=\text{ 2}\times radius \\ =2\times13.5=27 \\ \text{Diameter of circle C=27mm} \end{gathered}[/tex]
Therefore the diameter of the circle is 27mm
