Find the product :

$\dfrac{5}{-18} \times \dfrac{-9}{20}$

The product of two rational numbers $\dfrac{a}{b} \text{ and } \dfrac{c}{d}$ is given by $\dfrac{a}{b} \times \dfrac{c}{d} = \dfrac{a \times c}{b \times d}$.

Multiplying,

$\dfrac{5}{-18} \times \dfrac{-9}{20} = \dfrac{5 \times (-9)}{(-18) \times 20} \\[1em] = \dfrac{-45}{-360} \\[1em] = \dfrac{1}{8}$

Hence, $\mathbf{\dfrac{5}{-18} \times \dfrac{-9}{20} = \dfrac{1}{8}}$.