Find the area of a sector with a central angle of 180° and a diameter of 5.6 cm. round to the nearest tenth.

We calculate first for the area of the circle by the equation, 
                               Area = πD²/4
Substituting, 
                                Area = π(5.6 cm)²/4 = 24.63 cm²
Then, we multiply this value by the ratio of the given angle to the angle of one whole revolution,
                           Area of sector = (24.63 cm²)(180/360) = 12.315 cm²
Therefore, the area of the sector is approximately 12.315 cm².