Find the degree measure corresponding to the following radian measure (Write the answer without degree symbol)

$\frac{2\pi }{5}$

Find the degree measure corresponding to the following radian measure. (Write the answer without degree symbol)

$\frac{7\pi }{3}$

Find the degree measure corresponding to the following radian measure. (Write the answer without degree symbol)

$\frac{10\pi }{9}$

If in two circles, arcs of the same length subtend angles $60°$ and $75°$ at the centre, find the ratio of their radii.  [Write the answer in fraction]