A trapezoidal vegetable field has an upper base of 24 meters, a lower base of 36 meters, and a height of 18 meters. Find the area of this vegetable field.
一块梯形菜地，上底是24米，下底是36米，高18米，求这块菜地的面积．
<gadget id="calculator">24 + 36</gadget>
<output>60</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">60 * 9</gadget>
<output>540</output>

<result>540</result>