Assertion : If the distance between parallel plates of a capacitor is halved and dielectric constant is three times, then the capacitance becomes 6 times.
Reason : Capacitance of the capacitor does not depend upon the nature of the dielectric material.

Assertion is correct but Reason is incorrect.

C = ε_oA/d and C = Kε_oA/d if a material of dielectric constant K is inserted between the plates.

$\frac{C_1}{C_2} = \frac{K_1}{K_2} \frac{d_2}{d_1} = \frac{1}{2} \frac{1}{3} = \frac{1}{6}$

$ C_2 = 6 C_1$