A rhombus and its diagonals form four congruent right triangles with legs that are each one-half the measure of one of the diagonals and the hypotenuse equal in measure to one of the sides of the rhombus.
So, half of 12 is 6 and half of 16 is 8, so the measure of the side of the rhombus must be:
And, like a square, the perimeter of a rhombus is 4 times the measure of one side, so:
