Given:
Diagonals of the rhombus are:
- 8 cm
- 8 mm
- 6 cm
- 5 mm

To find:
The area of the rhombus

Approach:
To find the area of a rhombus, we can use the formula:

Area = (d1 * d2) / 2

Where:
- d1 and d2 are the lengths of the diagonals

Conversion:
Before calculating the area, let's convert the given measurements to a consistent unit. Since the diagonals are given in both centimeters and millimeters, let's convert all the measurements to millimeters.

- 8 cm = 8 * 10 mm = 80 mm
- 6 cm = 6 * 10 mm = 60 mm

Now we have the diagonals in the same unit: 80 mm, 8 mm, 60 mm, and 5 mm.

Calculating the area:
Using the formula mentioned earlier, we can calculate the area of the rhombus.

Area = (d1 * d2) / 2

Area = (80 mm * 8 mm) / 2

Area = 640 mm²

Therefore, the area of the rhombus is 640 mm².

Summary:
The area of the rhombus with diagonals 8 cm, 8 mm, 6 cm, and 5 mm is 640 mm².