Write each of the following rational numbers with positive denominator :

(i) $\dfrac{16}{-21}$

(ii) $\dfrac{1}{-5}$

(iii) $\dfrac{-7}{-12}$

(iv) $\dfrac{5}{-1}$

(v) $\dfrac{-6}{-1}$

(i) We have:

$\dfrac{16}{-21} = \dfrac{16 \times (-1)}{-21 \times (-1)} = \dfrac{-16}{21}$

∴ The rational number with a positive denominator is $\dfrac{-16}{21}$.

(ii) We have:

$\dfrac{1}{-5} = \dfrac{1 \times (-1)}{-5 \times (-1)} = \dfrac{-1}{5}$

∴ The rational number with a positive denominator is $\dfrac{-1}{5}$.

(iii) We have:

$\dfrac{-7}{-12} = \dfrac{(-7) \times (-1)}{(-12) \times (-1)} = \dfrac{7}{12}$

∴ The rational number with a positive denominator is $\dfrac{7}{12}$.

(iv) We have:

$\dfrac{5}{-1} = \dfrac{5 \times (-1)}{-1 \times (-1)} = \dfrac{-5}{1}$

∴ The rational number with a positive denominator is $\dfrac{-5}{1}$.

(v) We have:

$\dfrac{-6}{-1} = \dfrac{(-6) \times (-1)}{-1 \times (-1)} = \dfrac{6}{1}$

∴ The rational number with a positive denominator is $\dfrac{6}{1}$.