If the perimeter of a diamond is 20cm and the length of a diagonal is 8cm, what is its area?

If the perimeter of a diamond is 20cm and the length of a diagonal is 8cm, what is its area?

The perimeter is 20cm, so the side length is 5cm. One diagonal line is 8cm. According to Pythagorean theorem, the other diagonal line is 6cm. So the area is 24cm square