$\displaystyle r= \frac{1}{6}l$\displaystyle r= \frac{1}{6}l

$\displaystyle r= \frac{1}{4}l$\displaystyle r= \frac{1}{4}l

$\displaystyle r= \frac{1}{3}l$\displaystyle r= \frac{1}{3}l

$\displaystyle r= \frac{1}{2}l$\displaystyle r= \frac{1}{2}l