Answer: The area of the rhombus is 9.6 cm.
To start, we can find the area of the square. 6 x 6 = 36 cm^2
Since the area of the rhombus is 4/5 of the area of the square, we multiply 36 by 0.8 = 28.8 cm^2 is the area of the rhombus.
Now, use the area formula for a rhombus to find the height of the rhombus.
A = 0.5bh
28.8 = 0.5(6)h
9.6 = h