Solution: Since $\angle AOB = 90^\circ$, $\overrightarrowOA \cdot \overrightarrowOB = 0$. Compute $\|\overrightarrowOC\|^2 = 4\|\overrightarrowOA\|^2 + \|\overrightarrowOB\|^2 - 4\overrightarrowOA \cdot \overrightarrowOB = 4(4) + 9 - 0 = 25$. Thus, $\|\overrightarrowOC\| = 5$. - Crosslake