trapezoidal flowerbed with an upper base of 18 meters, a lower base of 25 meters and a height of 20 meters. How many square meters is this garden?
一块梯形花圃，上底18米，下底25米，高20米．这块花圃有多少平方米？
<gadget id="calculator">18 + 25</gadget>
<output>43</output>

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

<gadget id="calculator">43 * 10</gadget>
<output>430</output>

<result>430</result>