What number should be subtracted from $-\dfrac{2}{3}$ to get $-\dfrac{1}{6}$?

[Hint: Required number = $\dfrac{-2}{3} - \left(-\dfrac{1}{6}\right)$]

State whether each of the following statements is true or false:

(i) The difference of two rational numbers is always a rational number.

(ii) $\dfrac{2}{3} - \dfrac{3}{5} = \dfrac{3}{5} - \dfrac{2}{3}$

(iii) 1 is the additive identity for rational numbers.

(iv) Subtraction is commutative on rational numbers.

(v) There exists a rational number which is its own additive inverse.

(vi) $\dfrac{19}{-5} + \dfrac{-3}{11} = \dfrac{19}{5} + \dfrac{3}{11}$

Find the product :

$-9 \times \dfrac{7}{18}$

Find the product :

$\dfrac{-3}{16} \times \dfrac{8}{-15}$