[tex]\textit{arc's length}\\\\ s = \cfrac{\theta \pi r}{180} ~~ \begin{cases} r=radius\\ \theta =\stackrel{degrees}{angle}\\[-0.5em] \hrulefill\\ \theta = 100\\ s=28 \end{cases}\implies 28=\cfrac{(100)\pi r}{180}\implies 28=\cfrac{5\pi r}{9} \\\\\\ 252=5\pi r\implies \cfrac{252}{5\pi }=r\implies 16.04\approx r[/tex]
