A trapezoidal wheat field has an upper base of 21.6 meters, a lower base of 31.8 meters, and a height of 16 meters. What is the area of this wheat field?
一块梯形麦地，上底是21.6米，下底是31.8米，高是16米．这块麦地的面积是多少？
<gadget id="calculator">21.6 + 31.8</gadget>
<output>53.4</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">53.4 * 8</gadget>
<output>427.2</output>

<result>427.2</result>