Answer
Let us look through the two pairs of sunglasses at the same time and rotate one pair $60^{\circ}$ to the other. If both pairs are polarized, the overlapping lenses will become darker, if this does not happen, atleast one pair is not polarized.
Work Step by Step
Let us look through the two pairs of sunglasses at the same time and rotate one pair $60^{\circ}$ to the other. If both pairs are polarized, the overlapping lenses will become darker, if this does not happen, atleast one pair is not polarized.