Find the ratio compounded of the duplicate ratio of 5 : 6, the reciprocal ratio of 25 : 42 and the sub-duplicate ratio of 36 : 49.

Ratio compounded of the duplicate ratio of 5 : 6, the reciprocal ratio of 25 : 42 and the sub-duplicate ratio of 36 : 49,

$\Rightarrow \dfrac{5^2}{6^2} \times \dfrac{\dfrac{1}{25}}{\dfrac{1}{42}} \times \dfrac{\sqrt{36}}{\sqrt{49}} \\[1em] \Rightarrow \dfrac{25}{36} \times \dfrac{42}{25} \times \dfrac{6}{7} \\[1em] \Rightarrow \dfrac{1}{1}.$

Hence, resultant ratio = 1 : 1.