If third proportion of 3 and x is 27 and the third proportion of 2 and y is 8, find x : y.

9 : 4

Third proportion of a, b = $\frac{b\; \times\; b}{a}$

Third proportion of 3 and $x$ = $\frac{x\; \times\; x}{3}$ = 27

                                              $x^2$ = 81

                                               $x$ = 9

Third proportion of 2, $y$ = $\frac{y\; \times\; y}{2}$ = 8

                                                $y^2$ = 16

                                                $y$ = 4

Thus, x : y = 9 : 4