The side of a rhombus s and half the lengths of the 2 diagonals form a right-angled triangle. s^2 = 3^2 + 4^2 => length of side s = 5 cm.
Length of side of rhombus s = 5 cm, Perimeter of rhombus = 4(5) = 20cm.
But the answer you’re looking for is s=5