Incorrect. In the diagram, $\displaystyle{\overline{{{C}{D}}}}\usepackage{cmbright}\Huge\$ is a diameter of the circle and $\displaystyle{\overline{{{A}{B}}}}\usepackage{cmbright}\Huge\$ is a radius. The length of $\displaystyle{\overline{{{C}{D}}}}\usepackage{cmbright}\Huge\$ is given as 24 millimeters. Use the formula $\displaystyle{r}=\frac{{1}}{{2}}{d}\usepackage{cmbright}\Huge\$ to find the length of $\displaystyle{\overline{{{A}{B}}}}\usepackage{cmbright}\Huge\$ .