The barrage of a hydropower station has a trapezoidal cross-section, its upper base is 24 meters, the lower base is twice as long as the upper base, and its height is 20 meters. What is the area of this cross section in square meters?
有一座水电站的拦河坝的横截面是梯形，它的上底是24米，下底是上底的2倍，高是20米．这个横截面的面积是多少平方米？
<gadget id="calculator">24 * 2</gadget>
<output>48</output>

<gadget id="calculator">24 + 48</gadget>
<output>72</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">72 * 10</gadget>
<output>720</output>

<result>720</result>