Explanation:
a parallelogram has 2 pairs of equation sides (as a rectangle, just not necessarily with the 90° angles).
so, when one side is 16 cm, then there is a second side with 16cm.
the perimeter is the sum of all 4 sides (the 2 pairs of sides) : 48 cm.
and we know the length of one of these pairs : 2×16 = 32 cm.
what is left for the second pair of sides ?
48 - 32 = 16 cm
so, these 16 cm is the sum of a pair of equally long sides. that means their are
16/2 = 8 cm
long each.
so, the length of the "remaining" side is 8 cm.