[Described quadrilaterals] [Area of a quadrilateral]

The sum of two opposite sides of a circumscribed quadrilateral is 20, and the radius of the inscribed circle is 4. Find the area of the quadrilateral.
Apply the property of a circumscribed quadrilateral.

## Solution

Since the sums of the opposite sides of a circumscribed quadrilateral are equal, its semiperimeter is 20. Therefore, the desired area is $20 \cdot 4=80$.

## Answer

80.